instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
BrDGrTD, PBHDGrDw
answer:
DGr


question:
nWTnWqkLqYTBxT, cSTnWqkLqYwXmxRF
answer:
TnWqkLqY


question:
BPERYYrKqctkGzKSZS, QZTopYYrKqctrAx
answer:

YYrKqct