instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
NxgzLSzFGa, JvLzLSzsuj
answer:
zLSz


question:
fAsWQxuyBevvLogrSrgg, tmdBEUxuyBevvLogXjiMCbh
answer:
xuyBevvLog


question:
ZKMRTxCxbsbX, iovHrMRTxCxbsjv
answer:

MRTxCxbs