instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
DQVkAbWTTPhoBx, TeWTTPhonxcIKL
answer:
WTTPho


question:
yiKkIxbKvNk, znaIxbKggg
answer:
IxbK


question:
uLsCzpPBJqbQ, kyPzpPBtl
answer:

zpPB