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

Example Input: MvALRGKkpALcKdhTtnm, neMkRGKkpALcKdcaxnXEPxW
Example Output: RGKkpALcKd

Example Input: tyVlHfTPLRSdFilXnSfqQ, bkTPLRSdFiMgXC
Example Output: TPLRSdFi

Example Input: vAgakPJvEKraqbaoewaU, rmwDvEKraqbBrPQ
Example Output:
vEKraqb