instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ZKMRTxCxbsbX, iovHrMRTxCxbsjv
answer:
MRTxCxbs


question:
jkGcUm, dxGcSI
answer:
Gc


question:
IBkBJE, spkBTz
answer:

kB