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

[EX Q]: mXHhaCEIwqwEZcz, JZPXbYHhaCEIwZmna
[EX A]: HhaCEIw

[EX Q]: ssKUiWgGqsXYlFOOc, JDcVTmCgGqsXYlxYE
[EX A]: gGqsXYl

[EX Q]: ooQYEwIfxCBdaeOQKOnLB, rPmzEvdzJQYEwIfxCBdwS
[EX A]:
QYEwIfxCBd