instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ahPbomjSH, rBbomynK
answer:
bom


question:
slTUxy, oqTUYa
answer:
TU


question:
OkfQcCXH, QYfQcCeud
answer:

fQcC