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

ZyrpGdXvvtrKQIxU, CLNGdXvvtrKQDpicfqLdt
GdXvvtrKQ

oGaGjsaKsUpLQAg, iDGjsaKsUoYGuta
GjsaKsU

brHabHKyAggNnYOH, GEvSMExWCabHKyAggNnFcnJxxSqA

abHKyAggNn