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

Example Input: yJRITYgVTSNsPjG, NSIdKYgVTSNmj
Example Output: YgVTSN

Example Input: YKpdeJQhzyYiPoODACUu, mjmnIlCehzyYiPoOzZ
Example Output: hzyYiPoO

Example Input: EJwMwRpTuvPxUn, pPTRpTuvUuj
Example Output:
RpTuv