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

[EX Q]: HiEuutntEBpU, fdkqEuutntEBABdGZRND
[EX A]: EuutntEB

[EX Q]: RMurrwPjlfG, QBKrrwPDkTM
[EX A]: rrwP

[EX Q]: SuTXfSIkRGFV, gKfSIkZch
[EX A]:
fSIk