user26504: 
From the above position, black player lost (by mistakes) all of its pieces after his 15th move. How many more moves shall the black king have before it is checkmated by white if it is black' move?

user11144: It's a mate in 6. (EDIT: I was reminded Black is to move, but it is still #6 on any defense, if I checked correctly.) Stockfish can tell you, and any problem chess program can tell you exactly. For the lulz, here is the complete output of "Popeye" with the threat (White to move). tl;dr: Only 1.e4 mates in 6, which I remembered correctly, since this is a well-known chess problem.
   1.e2-e4 ! threat:
      2.Qd1-g4 threat:
              3.Qg4-g7 threat:
                      4.Bf1-b5 +
                          4...Ke8-d8
                              5.Qg7-d7 #
                  3...Ke8-d8
                      4.Bf1-a6 zugzwang.
                          4...Kd8-e8
                              5.Ba6-b5 +
                                  5...Ke8-d8
                                      6.Qg7-d7 #
                              5.Ba6-c8 zugzwang.
                                  5...Ke8-d8
                                      6.Qg7-d7 #
                      4.Bf1-b5 threat:
                              5.Qg7-d7 #
                          4...Kd8-c8
                              5.Bb5-c6 zugzwang.
                                  5...Kc8-b8
                                      6.Qg7-b7 #
                                  5...Kc8-d8
                                      6.Qg7-d7 #
                              5.Qg7-a7 zugzwang.
                                  5...Kc8-d8
                                      6.Qa7-d7 #
          2...Ke8-f7
              3.Qg4-d7 +
                  3...Kf7-g6
                      4.d2-d4 threat:
                              5.Qd7-e7 zugzwang.
                                  5...Kg6-h5
                                      6.Qe7-g5 #
                          4...Kg6-h5
                              5.Bf1-c4 zugzwang.
                                  5...Kh5-g6
                                      6.Qd7-f7 #
                                  5...Kh5-h4
                                      6.Qd7-h3 #
                              5.Qd7-f5 +
                                  5...Kh5-h4
                                      6.Qf5-h3 #
                                      6.Qf5-g5 #
                                      6.g2-g3 #
                                      6.Sg1-f3 #
                              5.Qd7-e6 zugzwang.
                                  5...Kh5-h4
                                      6.Qe6-h3 #
                              5.Qd7-h7 +
                                  5...Kh5-g4
                                      6.Qh7-h3 #
                                      6.h2-h3 #
                                      6.f2-f3 #
                                      6.Bf1-e2 #
                              5.Qd7-g7 threat:
                                      6.Qg7-g5 #
                          4...Kg6-f6
                              5.Bf1-c4 threat:
                                      6.Qd7-f7 #
                  3...Kf7-g8
                      4.b2-b4 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.b2-b3 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.d2-d4 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
                  3...Kf7-f6
                      4.d2-d4 threat:
                              5.Bf1-c4 threat:
                                      6.Qd7-f7 #
                          4...Kf6-g6
                              5.Qd7-e7 zugzwang.
                                  5...Kg6-h5
                                      6.Qe7-g5 #
                      4.d2-d3 zugzwang.
                          4...Kf6-e5
                              5.Qd7-c6 threat:
                                      6.Sg1-f3 #
                              5.Qd7-e7 +
                                  5...Ke5-d4
                                      6.Qe7-d6 #
                                      6.c2-c3 #
                                      6.Sg1-f3 #
                                      6.Sg1-e2 #
                                      6.Bc1-e3 #
                          4...Kf6-g6
                              5.Qd7-e7 zugzwang.
                                  5...Kg6-h5
                                      6.Qe7-g5 #
                  3...Kf7-f8
                      4.Sg1-h3 zugzwang.
                          4...Kf8-g8
                              5.Sh3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.Sg1-f3 zugzwang.
                          4...Kf8-g8
                              5.Sf3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.b2-b4 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.b2-b3 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.d2-d4 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
          2...Ke8-f8
              3.Bf1-b5 zugzwang.
                  3...Kf8-e7
                      4.Qg4-g6 zugzwang.
                          4...Ke7-f8
                              5.e4-e5 zugzwang.
                                  5...Kf8-e7
                                      6.Qg6-e8 #
                                      6.Qg6-f6 #
                          4...Ke7-d8
                              5.Qg6-d6 +
                                  5...Kd8-c8
                                      6.Bb5-a6 #
                  3...Kf8-f7
                      4.e4-e5 zugzwang.
                          4...Kf7-e7
                              5.Qg4-f5 threat:
                                      6.Qf5-f6 #
                                  5...Ke7-d8
                                      6.Qf5-d7 #
                          4...Kf7-f8
                              5.Qg4-g6 zugzwang.
                                  5...Kf8-e7
                                      6.Qg6-e8 #
                                      6.Qg6-f6 #
              3.Qg4-d7 threat:
                      4.Sg1-h3 zugzwang.
                          4...Kf8-g8
                              5.Sh3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.Sg1-f3 zugzwang.
                          4...Kf8-g8
                              5.Sf3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.b2-b4 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.b2-b3 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.d2-d4 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                  3...Kf8-g8
                      4.b2-b4 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.b2-b3 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.d2-d4 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
              3.Qg4-e6 threat:
                      4.Bf1-c4 threat:
                              5.Qe6-f7 #
                          4...Kf8-g7
                              5.d2-d4 threat:
                                      6.Qe6-h6 #
                                  5...Kg7-f8
                                      6.Qe6-f7 #
                                      6.Bc1-h6 #
                              5.d2-d3 threat:
                                      6.Qe6-h6 #
                                  5...Kg7-f8
                                      6.Qe6-f7 #
                                      6.Bc1-h6 #
                              5.Qe6-f7 +
                                  5...Kg7-h6
                                      6.d2-d4 #
                                      6.d2-d3 #
                                  5...Kg7-h8
                                      6.Qf7-g8 #
                      4.d2-d4 threat:
                              5.Bc1-h6 #
                          4...Kf8-g7
                              5.Bf1-c4 threat:
                                      6.Qe6-h6 #
                                  5...Kg7-f8
                                      6.Qe6-f7 #
                                      6.Bc1-h6 #
              3.Qg4-g6 zugzwang.
                  3...Kf8-e7
                      4.Bf1-b5 zugzwang.
                          4...Ke7-f8
                              5.e4-e5 zugzwang.
                                  5...Kf8-e7
                                      6.Qg6-e8 #
                                      6.Qg6-f6 #
                          4...Ke7-d8
                              5.Qg6-d6 +
                                  5...Kd8-c8
                                      6.Bb5-a6 #


26504: <p><a href="https://i.stack.imgur.com/ErniZ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ErniZ.png" alt="enter image description here" /></a></p>
<p>From the above position, black player lost (by mistakes) all of its pieces after his 15th move. How many more moves shall the black king have before it is checkmated by white if it is black' move?</p>
 11144: <p>It's a mate in 6. (EDIT: I was reminded Black is to move, but it is still #6 on any defense, if I checked correctly.) Stockfish can tell you, and any problem chess program can tell you exactly. For the lulz, here is the complete output of &quot;Popeye&quot; with the threat (White to move). tl;dr: Only 1.e4 mates in 6, which I remembered correctly, since this is a well-known chess problem.</p>
<pre><code>   1.e2-e4 ! threat:
      2.Qd1-g4 threat:
              3.Qg4-g7 threat:
                      4.Bf1-b5 +
                          4...Ke8-d8
                              5.Qg7-d7 #
                  3...Ke8-d8
                      4.Bf1-a6 zugzwang.
                          4...Kd8-e8
                              5.Ba6-b5 +
                                  5...Ke8-d8
                                      6.Qg7-d7 #
                              5.Ba6-c8 zugzwang.
                                  5...Ke8-d8
                                      6.Qg7-d7 #
                      4.Bf1-b5 threat:
                              5.Qg7-d7 #
                          4...Kd8-c8
                              5.Bb5-c6 zugzwang.
                                  5...Kc8-b8
                                      6.Qg7-b7 #
                                  5...Kc8-d8
                                      6.Qg7-d7 #
                              5.Qg7-a7 zugzwang.
                                  5...Kc8-d8
                                      6.Qa7-d7 #
          2...Ke8-f7
              3.Qg4-d7 +
                  3...Kf7-g6
                      4.d2-d4 threat:
                              5.Qd7-e7 zugzwang.
                                  5...Kg6-h5
                                      6.Qe7-g5 #
                          4...Kg6-h5
                              5.Bf1-c4 zugzwang.
                                  5...Kh5-g6
                                      6.Qd7-f7 #
                                  5...Kh5-h4
                                      6.Qd7-h3 #
                              5.Qd7-f5 +
                                  5...Kh5-h4
                                      6.Qf5-h3 #
                                      6.Qf5-g5 #
                                      6.g2-g3 #
                                      6.Sg1-f3 #
                              5.Qd7-e6 zugzwang.
                                  5...Kh5-h4
                                      6.Qe6-h3 #
                              5.Qd7-h7 +
                                  5...Kh5-g4
                                      6.Qh7-h3 #
                                      6.h2-h3 #
                                      6.f2-f3 #
                                      6.Bf1-e2 #
                              5.Qd7-g7 threat:
                                      6.Qg7-g5 #
                          4...Kg6-f6
                              5.Bf1-c4 threat:
                                      6.Qd7-f7 #
                  3...Kf7-g8
                      4.b2-b4 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.b2-b3 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.d2-d4 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
                  3...Kf7-f6
                      4.d2-d4 threat:
                              5.Bf1-c4 threat:
                                      6.Qd7-f7 #
                          4...Kf6-g6
                              5.Qd7-e7 zugzwang.
                                  5...Kg6-h5
                                      6.Qe7-g5 #
                      4.d2-d3 zugzwang.
                          4...Kf6-e5
                              5.Qd7-c6 threat:
                                      6.Sg1-f3 #
                              5.Qd7-e7 +
                                  5...Ke5-d4
                                      6.Qe7-d6 #
                                      6.c2-c3 #
                                      6.Sg1-f3 #
                                      6.Sg1-e2 #
                                      6.Bc1-e3 #
                          4...Kf6-g6
                              5.Qd7-e7 zugzwang.
                                  5...Kg6-h5
                                      6.Qe7-g5 #
                  3...Kf7-f8
                      4.Sg1-h3 zugzwang.
                          4...Kf8-g8
                              5.Sh3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.Sg1-f3 zugzwang.
                          4...Kf8-g8
                              5.Sf3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.b2-b4 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.b2-b3 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.d2-d4 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
          2...Ke8-f8
              3.Bf1-b5 zugzwang.
                  3...Kf8-e7
                      4.Qg4-g6 zugzwang.
                          4...Ke7-f8
                              5.e4-e5 zugzwang.
                                  5...Kf8-e7
                                      6.Qg6-e8 #
                                      6.Qg6-f6 #
                          4...Ke7-d8
                              5.Qg6-d6 +
                                  5...Kd8-c8
                                      6.Bb5-a6 #
                  3...Kf8-f7
                      4.e4-e5 zugzwang.
                          4...Kf7-e7
                              5.Qg4-f5 threat:
                                      6.Qf5-f6 #
                                  5...Ke7-d8
                                      6.Qf5-d7 #
                          4...Kf7-f8
                              5.Qg4-g6 zugzwang.
                                  5...Kf8-e7
                                      6.Qg6-e8 #
                                      6.Qg6-f6 #
              3.Qg4-d7 threat:
                      4.Sg1-h3 zugzwang.
                          4...Kf8-g8
                              5.Sh3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.Sg1-f3 zugzwang.
                          4...Kf8-g8
                              5.Sf3-g5 zugzwang.
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Qd7-h7 #
                      4.b2-b4 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.b2-b3 threat:
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kf8-g8
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                      4.d2-d4 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 +
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                  3...Kf8-g8
                      4.b2-b4 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.b2-b3 threat:
                              5.Bf1-c4 +
                                  5...Kg8-f8
                                      6.Qd7-f7 #
                                      6.Bc1-a3 #
                                  5...Kg8-h8
                                      6.Bc1-b2 #
                          4...Kg8-f8
                              5.Bc1-b2 zugzwang.
                                  5...Kf8-g8
                                      6.Qd7-g7 #
                          4...Kg8-h8
                              5.Bc1-b2 +
                                  5...Kh8-g8
                                      6.Qd7-g7 #
                      4.d2-d4 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
                      4.d2-d3 threat:
                              5.Bc1-h6 threat:
                                      6.Qd7-g7 #
              3.Qg4-e6 threat:
                      4.Bf1-c4 threat:
                              5.Qe6-f7 #
                          4...Kf8-g7
                              5.d2-d4 threat:
                                      6.Qe6-h6 #
                                  5...Kg7-f8
                                      6.Qe6-f7 #
                                      6.Bc1-h6 #
                              5.d2-d3 threat:
                                      6.Qe6-h6 #
                                  5...Kg7-f8
                                      6.Qe6-f7 #
                                      6.Bc1-h6 #
                              5.Qe6-f7 +
                                  5...Kg7-h6
                                      6.d2-d4 #
                                      6.d2-d3 #
                                  5...Kg7-h8
                                      6.Qf7-g8 #
                      4.d2-d4 threat:
                              5.Bc1-h6 #
                          4...Kf8-g7
                              5.Bf1-c4 threat:
                                      6.Qe6-h6 #
                                  5...Kg7-f8
                                      6.Qe6-f7 #
                                      6.Bc1-h6 #
              3.Qg4-g6 zugzwang.
                  3...Kf8-e7
                      4.Bf1-b5 zugzwang.
                          4...Ke7-f8
                              5.e4-e5 zugzwang.
                                  5...Kf8-e7
                                      6.Qg6-e8 #
                                      6.Qg6-f6 #
                          4...Ke7-d8
                              5.Qg6-d6 +
                                  5...Kd8-c8
                                      6.Bb5-a6 #
</code></pre>
