this year Chunin Selection Exam hold Konoha take n ninjas name s_1 s_2 s_n all name distinct one exam stage consists fight participant this year rule determine ninjas fight follow ninjas j fight follow condition hold neq j s_j substre s_i k j s_j substring s_k s_k substre s_i a string substre string b obtain b deletion possibly zero character begin possibly zero character endyour task find fight go place year