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

Ex Input:
zBNTHKtofMdHfBgJhOfojzM, VIkVdFapofMdHfBgjPCUo

Ex Output:
ofMdHfBg


Ex Input:
RwqzMTeLMdPx, qaWtYhqzMTeLMdHbWDT

Ex Output:
qzMTeLMd


Ex Input:
bxqOxH, qZqOVW

Ex Output:

qO