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

Example Input: ugDpSMRvHM, DDwSMRvxw
Example Output: SMRv

Example Input: pqFpUjQGiofBOjfYkRW, pQMnCFlhFpUjQGiofbc
Example Output: FpUjQGiof

Example Input: pGUglqRdkZkhHADadyOWsuksElxY, JbfwdLfvZkhHADadyOcihf
Example Output:
ZkhHADadyO