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

XbjDHRCWxdPbhibUKn, SrpuPDHRCWxdPbKPWEXNWbZ
DHRCWxdPb

HKCoXQsLRtowYJ, PGRzNUQsLRtoLcqkn
QsLRto

LTAAhTrXBoPuBTmQW, TJZcpglBnAAhTrXBoPubOahXJT

AAhTrXBoPu