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

Example Input: TUAHhdvHIBxogI, LjfGsAHhdvHJcSdNV
Example Output: AHhdvH

Example Input: yiKkIxbKvNk, znaIxbKggg
Example Output: IxbK

Example Input: xpwqfeptCXMiDstCmSDs, dcFiPveptCXMiDstWflLaKuH
Example Output:
eptCXMiDst