instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
BUvWkxrAvDQG, rHrkxrAkCE
answer:
kxrA


question:
vISTrmBMpQyanUTSXUCm, dJGyOHMpQyanUTpSb
answer:
MpQyanUT


question:
yDawTNwvmn, ZXWwTNwmlcc
answer:

wTNw