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

zqRbqwgmqGIAGTeeoGFOSr, RFnLqwgmqGIAGLcEvAWxY
qwgmqGIAG

pBDnbfrAxJfVhPBxheXZGp, LMtorAxJfVhPnnaed
rAxJfVhP

wfWNUsQi, rlWNUtPe

WNU