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

Example Input: JXnHYuZvAYK, zhUYuZvASGhd
Example Output: YuZvA

Example Input: OezHeoe, ouUzHemU
Example Output: zHe

Example Input: DVObgaYpiFPSaNmhN, wJJwdpiFPSaNLfyQLT
Example Output:
piFPSaN