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

PQSFjlnU, kTSFjMUh
SFj

mjCEUoPmeKbvCgUtUL, SrHtrPmeKbvYpQAVp
PmeKbv

rSXbboHPUfgceelpKJLQLgx, ZwPUfgceelpDXm

PUfgceelp