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

cfvqbAUpWEmhCSFaUvGrYVNGeUiRP, hAxWMEmhCSFaUvGLBLmdTxhy
EmhCSFaUvG

RMurrwPjlfG, QBKrrwPDkTM
rrwP

HtlPqnwuupGeA, XNrMjnwuupGBd

nwuupG