instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
RwduMBkDazrwZP, UPzcwtWMBkDazrAw
answer:
MBkDazr


question:
DZfOjrQffR, CXOjrQQc
answer:
OjrQ


question:
yOvHJk, vUvHSC
answer:

vH