instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
YRNpKFPGzUsgCOBJgbVG, TdEpMngFPGzUsgCOZykYRrLp
answer:
FPGzUsgCO


question:
NxgzLSzFGa, JvLzLSzsuj
answer:
zLSz


question:
BieGNJhimltAOGJfLm, bchFJkQNimltAOGJfelF
answer:

imltAOGJf