instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
jkGcUm, dxGcSI
answer:
Gc


question:
TizkNtJUPHfhmGQ, enzehVkNtJUPHunpG
answer:
kNtJUPH


question:
sEYtoQlG, XIstoQQPw
answer:

toQ