instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
GoodBOwvrki, kRCsdBOwvrakgiH
answer:
dBOwvr

question:
RinootTGLjbRGYznmBdH, oRMtTGLjbRGYzwEVHsjW
answer:
tTGLjbRGYz

question:
qYEgtpTVADd, ugdxEgtpTbDTiG
answer:
EgtpT