instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
cvZfWOwa, xOfWOhZs
answer:
fWO


question:
libDFDxIgRiglWfxMVRr, yMltDxIgRiglpms
answer:
DxIgRigl


question:
iPdoVatHbgcKZyi, kVDkftHbgcKiOddb
answer:

tHbgcK


