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

wkVVZREWhcSCpvCTB, ZQWhcSCpvCDVUY
WhcSCpvC

YRNpKFPGzUsgCOBJgbVG, TdEpMngFPGzUsgCOZykYRrLp
FPGzUsgCO

VGRjWGHRcBdFmkVg, eSwqALQXWGHRcBdFsDXCM

WGHRcBdF