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

[EX Q]: oDdulHNcCdgbRGxiBTxM, kDcCdgbRGnsJlvas
[EX A]: cCdgbRG

[EX Q]: XwBMFIV, SNLBMFZQ
[EX A]: BMF

[EX Q]: TIIEIbQZM, MXEIbswy
[EX A]:
EIb