instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
OyXwTWbLByC, yODnTWbLWYzc
answer:
TWbL


question:
xzMUdHcoYJFWLOILjrg, vCscoYJFWLzO
answer:
coYJFWL


question:
JqdTDnZqSuSVcMsx, TEtDDnZqSuZa
answer:

DnZqSu