instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
QeNePjbLBKbDOuAVTJtXL, xjPVOyPbLBKbDOuDsMSEF
answer:
bLBKbDOu


question:
uqDaPS, XyDaMZ
answer:
Da


question:
oHoJrr, YAoJSq
answer:

oJ