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

[Q]: fVEFJa, WtEFYK
[A]: EF


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


[Q]: YZQESBMLTHbEyviVD, EUUTrixLTHbEyvHy
[A]:
LTHbEyv