instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
kUoqCMPFTqGE, guoqCMPkwJs
answer:
oqCMP


question:
NmtypJ, tQtyZD
answer:
ty


question:
oChGVBrLziktltdQyOhfV, SoeeVaGziktltdQjb
answer:

ziktltdQ