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

[EX Q]: IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ
[EX A]: BpnullsPI

[EX Q]: HhBhJMpxpty, MxTJMpxnQEf
[EX A]: JMpx

[EX Q]: RHoMEAtfOQXuyZtVooE, oMVPmeVdEAtfOQXuyZZILWWVYAoj
[EX A]:
EAtfOQXuyZ