instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
iaXeqfIrYKxPJRXxfSm, rIYKxPJRXxfsjVsqe
answer:
YKxPJRXxf


question:
XZslQqrShfCXRXyHrFVq, BtOQgQqrShfCXRRCRbMvXPM
answer:
QqrShfCXR


question:
DpMUuE, exMUvd
answer:

MU