instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
vhZuXCsIkQR, YflCuXCsIkLu
answer:
uXCsIk


question:
QaxEaxdouNyyvNAn, wRjWSaxdouNyyrriQiG
answer:
axdouNyy


question:
XEbphNrTlAxO, wJbphNrfBL
answer:

bphNr