instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ZyrpGdXvvtrKQIxU, CLNGdXvvtrKQDpicfqLdt
answer:
GdXvvtrKQ


question:
kvutZfcPKzHE, kTKutZfcPTGmU
answer:
utZfcP


question:
UHjTdAnCKQTlEI, FtdLVnCKQTlrUKt
answer:

nCKQTl