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

Ex Input:
tmBlKUto, eFDBlKLy

Ex Output:
BlK


Ex Input:
XZslQqrShfCXRXyHrFVq, BtOQgQqrShfCXRRCRbMvXPM

Ex Output:
QqrShfCXR


Ex Input:
nReRhkwjDrHogE, rbeeRhkwjitXoAg

Ex Output:

eRhkwj