instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
lMRuEThD, wqQRuEKp
answer:
RuE


question:
SJIkEibGrqcrOBgGjYjJc, EervOGrqcrOBgGJZyx
answer:
GrqcrOBgG


question:
PeiXuowETnpVPO, eKXGJMjiXuowETNg
answer:

iXuowET