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

qMnjlfIsQRtUlPggCpHqu, gfVndMwYDIsQRtUlPgqBJKCX
IsQRtUlPg

tmBlKUto, eFDBlKLy
BlK

BpGFyhLez, DfFyhuJY

Fyh