instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
bdCOjNchdKtvWzOI, FwejNchdKhEd
answer:
jNchdK


question:
dlzequypR, Puequqv
answer:
equ


question:
QGJmeWMmhVQLRkGaDHaaBIYoJKD, vGujAmhVQLRkGaDSu
answer:

mhVQLRkGaD