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

[EX Q]: umXfmRnUgALpFAqBaKfNfo, aOAXWnUgALpFAqBmNpTCdj
[EX A]: nUgALpFAqB

[EX Q]: HaIPcFXLhYDp, AdIPcFXtJdRE
[EX A]: IPcFX

[EX Q]: XvrqdffXvQUkLHMC, MFedYJjIffXvQUkLHNLjRWbr
[EX A]:
ffXvQUkLH