instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
BmxgSFWBlVX, kGgKrgSFWBlGunFcZ
answer:
gSFWBl


question:
BUvWkxrAvDQG, rHrkxrAkCE
answer:
kxrA


question:
CUCatjSmlIPtkPRhab, lnFPatjSmlIPCKNR
answer:

atjSmlIP