instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
zqRbqwgmqGIAGTeeoGFOSr, RFnLqwgmqGIAGLcEvAWxY
answer:
qwgmqGIAG


question:
XMtSwZVAHsNYhbyDm, asAVAHsNYhSPuNLrV
answer:
VAHsNYh


question:
HHHrkBNWQFjvh, lPEvFHrkBNWQwiPw
answer:

HrkBNWQ