instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
ZyrpGdXvvtrKQIxU, CLNGdXvvtrKQDpicfqLdt
answer:
GdXvvtrKQ


question:
ykDpbd, YFDpmO
answer:
Dp


question:
GFVsYknVtDIaEPDzFRr, yfyDtDIaEPDzcBkhqxJ
answer:

tDIaEPDz