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

Q: uRLpAWCotLmxcSmKyvo, laotLmxcSmKyBwVfJB

A: otLmxcSmKy
****
Q: bmsrkXGb, GcarkXOZF

A: rkX
****
Q: uiaJtXHU, dCeJtXGiu

A:
JtX
****