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

[EX Q]: fREVIdeTcakgFnwDWTVev, IbtXImseeTcakgFnwDYsKBAlux
[EX A]: eTcakgFnwD

[EX Q]: oHoJrr, YAoJSq
[EX A]: oJ

[EX Q]: PYRaAH, bJRazt
[EX A]:
Ra