instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
BpGFyhLez, DfFyhuJY
answer:
Fyh


question:
VTwtMVKmrRvL, WLoVtWtMVKmrDCke
answer:
tMVKmr


question:
KXRzIgUFf, pDizIgkz
answer:

zIg