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

[EX Q]: STvKOHq, XMGvKOdyM
[EX A]: vKO

[EX Q]: BmxgSFWBlVX, kGgKrgSFWBlGunFcZ
[EX A]: gSFWBl

[EX Q]: eeXYrtjsEqFWSP, rzcKertjsEqOMDhmZ
[EX A]:
rtjsEq