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

zeuyZKwvIOfx, BlmZKwvspUt
ZKwv

zqRbqwgmqGIAGTeeoGFOSr, RFnLqwgmqGIAGLcEvAWxY
qwgmqGIAG

ctXXVoKglyr, BhupZXXVoKyXqUK

XXVoK