instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
eMDNXl, ZZDNAa
answer:
DN


question:
bOvlVNWf, iivlVzWt
answer:
vlV


question:
OwsNJaggT, RIjNJahU
answer:

NJa