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

zBxuZfJgYrlRSzkmAktO, YNMgYrlRSzklmBOH
gYrlRSzk

XZslQqrShfCXRXyHrFVq, BtOQgQqrShfCXRRCRbMvXPM
QqrShfCXR

BywClSrHITeihJOmXP, cmmAYfwClSrHITVSHSyVM

wClSrHIT