instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
mJoHBJehHtkFS, ZMrDxHBJehHtxS
answer:
HBJehHt


question:
vhZuXCsIkQR, YflCuXCsIkLu
answer:
uXCsIk


question:
zXrbVmHmPm, aBbVmHjjo
answer:

bVmH