instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
jFVaEHbMrrkW, ekfVaEHbPnBnM
answer:
VaEHb


question:
jinzsW, SMnzaW
answer:
nz


question:
XJDJsrwErIaHmYhudH, qtCDJsrwErIaxZ
answer:

DJsrwErIa