instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ztkWLUJQXxP, fYluOkWLUJKDX
answer:
kWLUJ


question:
oGaGjsaKsUpLQAg, iDGjsaKsUoYGuta
answer:
GjsaKsU


question:
BgBeDGEASoQxqhGgAcvSc, etSoQxqhGgdXr
answer:

SoQxqhGg