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

[EX Q]: xtCJGe, DXCJSw
[EX A]: CJ

[EX Q]: PShMbsbexXGlpBuMMDZZS, sVqGxSexXGlpBxuHXoI
[EX A]: exXGlpB

[EX Q]: rBkTelxrkVm, MwPelxrvwtO
[EX A]:
elxr