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

Example Input: IJQqdzqdaGEIcdyh, izlVdzqdaGGiPYz
Example Output: dzqdaG

Example Input: cfvqbAUpWEmhCSFaUvGrYVNGeUiRP, hAxWMEmhCSFaUvGLBLmdTxhy
Example Output: EmhCSFaUvG

Example Input: fYoWTcQCMMmAsdlvLbTAo, hendxCMMmAsdlJwQkvHm
Example Output:
CMMmAsdl