instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zqRbqwgmqGIAGTeeoGFOSr, RFnLqwgmqGIAGLcEvAWxY
answer:
qwgmqGIAG


question:
IGHhMfqLeBpnullsPInfBH, LTDBpnullsPIBynwCrCQ
answer:
BpnullsPI


question:
jiJSOMlidERqjFFN, AKjtNqMlidERqjFsXCycNhn
answer:

MlidERqjF