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

[EX Q]: CCzKRbuEAmN, qTLzKRbuhEqq
[EX A]: zKRbu

[EX Q]: GHdeqnuYnQ, zzQeqnutAZ
[EX A]: eqnu

[EX Q]: uRNaZZoUrCMfivLenmvNoLfLB, lhzUrCMfivLenGLbTHKBC
[EX A]:
UrCMfivLen