title: Finding a specific sum of elements from two arrays
body: <p>Could you please help me with this one? :
  "Let A and B are an incrementally ordered arrays of natural numbers and K be some arbitrary natural number. Find an effective algorithm which determines all possible pairs of indexes (i,j) such that A[i]+B[j]=K. Prove algorithm's correctness and estimate its complexity."</p>
  
  <p>Should I just iterate over the first array and do a binary search on the other one?
  Thanks :)</p>