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

Example Input: jdLbZSCzaAHGbNwILGmudOH, RdIPuEYJvUZSCzaAHGbNduLToRC
Example Output: ZSCzaAHGbN

Example Input: CUlMsvov, iflMsSRp
Example Output: lMs

Example Input: SFNuqSwgwEhkCp, rTmlqSwgwErrkSG
Example Output:
qSwgwE