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

Example Input: vMsEJRoLkWcmkuwNRz, ZmoLkWcmVZiBv
Example Output: oLkWcm

Example Input: PnRypl, HvRydi
Example Output: Ry

Example Input: GXyTIu, pdyTJE
Example Output:
yT