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

Ex Input:
oDdulHNcCdgbRGxiBTxM, kDcCdgbRGnsJlvas

Ex Output:
cCdgbRG


Ex Input:
HiGmCdXrmFRJYWLvZbpU, IxhkrmFRJYWLvZLaqRVxPkL

Ex Output:
rmFRJYWLvZ


Ex Input:
ziQfXgsMBh, cNQfXgsafllg

Ex Output:

QfXgs