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

Ex Input:
yRhCObvPZYoKUoQnyaatR, NHzLJYPZYoKUoQnJnIsZxC

Ex Output:
PZYoKUoQn


Ex Input:
ahPbomjSH, rBbomynK

Ex Output:
bom


Ex Input:
wIkjpHwztmXdbkrm, utMZUHwztmXhHbJ

Ex Output:

HwztmX