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

[EX Q]: QRPOwtZATjDoJDdRNNSOH, wiafFMwpAjDoJDdRNNuCDZ
[EX A]: jDoJDdRNN

[EX Q]: YRNpKFPGzUsgCOBJgbVG, TdEpMngFPGzUsgCOZykYRrLp
[EX A]: FPGzUsgCO

[EX Q]: iugHIXitDRaXJJyo, NRTkrHgHIXitDRXOSk
[EX A]:
gHIXitDR