instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
STvKOHq, XMGvKOdyM
answer:
vKO


question:
UovaYpHjYSQzrfsxRfvIZE, pUOFxIKOGQzrfsxRfvIjrza
answer:
QzrfsxRfvI


question:
RinootTGLjbRGYznmBdH, oRMtTGLjbRGYzwEVHsjW
answer:

tTGLjbRGYz