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

Example Input: JAfPtjqqUYMD, cpXItjqqFN
Example Output: tjqq

Example Input: HEVqGddewrNqiZ, iyvlddewrNXr
Example Output: ddewrN

Example Input: mUBlllktNpzy, ExMllktHP
Example Output:
llkt