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

iUtNuU, iKtNWk
tN

bUHPpvVtFQNSpUdg, zggEFoKBHPpvVtFQNHXsc
HPpvVtFQN

XifGDWFjkqOfm, kNFeDWFjkZf

DWFjk