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

[EX Q]: apGMPThLTCw, LvMPThYW
[EX A]: MPTh

[EX Q]: RtOkkgLvhgfGlX, vCOkgLvhzOa
[EX A]: kgLvh

[EX Q]: velaXjrnMmlpdHyaDKNzwYrYH, qjtgthErnMmlpdHyaeXAoVKrNKx
[EX A]:
rnMmlpdHya