In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.

Example Input: VTwtMVKmrRvL, WLoVtWtMVKmrDCke
Example Output: tMVKmr

Example Input: NUuLSmDjCKcJPc, lGGSLIDjCKcJBo
Example Output: DjCKcJ

Example Input: NmtypJ, tQtyZD
Example Output:
ty