instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
mmDhYqPJC, qThYqxW
answer:
hYq


question:
WFAPUCgVYbmZiFlacUzyv, xQFiekrgPUCgVYbmZUEtl
answer:
PUCgVYbmZ


question:
zktozmRkIyuFjXgG, AblDYTyOozmRkIyuFLcq
answer:

ozmRkIyuF