instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
yQRDycTycwH, ImycTycrR
answer:
ycTyc


question:
IJQqdzqdaGEIcdyh, izlVdzqdaGGiPYz
answer:
dzqdaG


question:
BfwVvutuPuS, yfEycvutuPeeu
answer:

vutuP