instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
xfZYYDKEqoRRu, ztCeYYDKEqoPG
answer:
YYDKEqo


question:
wNiHcaiUPHnjp, aSTmjcaiUPHFzOu
answer:
caiUPH


question:
pBflpErY, ASflpTT
answer:

flp