instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
kvutZfcPKzHE, kTKutZfcPTGmU
answer:
utZfcP


question:
yOGvgtAmwMwcIRtJ, cQtAmwMwcIRjfjO
answer:
tAmwMwcIR


question:
BoYCgSmVJXD, VZAjYCgSmKY
answer:

YCgSm