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

zqRbqwgmqGIAGTeeoGFOSr, RFnLqwgmqGIAGLcEvAWxY
qwgmqGIAG

GBTHKtWUzK, ovVNKtWUmVJF
KtWU

fXTnHVzILRbTacZP, ayLdhvHVzILRbFBtOvY

HVzILRb