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

Example Input: sEYtoQlG, XIstoQQPw
Example Output: toQ

Example Input: sdGIVJPsWWszKPCGk, ghRJPsWWszKcJUg
Example Output: JPsWWszK

Example Input: vYyrHfgtWTg, FpXHfgtWoUuV
Example Output:
HfgtW