instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
PivhPfah, XSghPfOi
answer:
hPf


question:
aeQjEeiWGONmzGimhGiw, RIEeiWGONmOZuVYr
answer:
EeiWGONm


question:
XEjdgDvC, ZKdgDkd
answer:

dgD