instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zRwQdelc, UdAUwQdejhe
answer:
wQde


question:
IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ
answer:
BpnullsPI


question:
qWJoYfTaItIWCj, LAJfTaItInenLKp
answer:

fTaItI