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

[EX Q]: zzEhnt, sYEhtc
[EX A]: Eh

[EX Q]: SJIkEibGrqcrOBgGjYjJc, EervOGrqcrOBgGJZyx
[EX A]: GrqcrOBgG

[EX Q]: oxLxyM, HyLxDx
[EX A]:
Lx