instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
kyADtWLlnmYv, tcaKvDtWLlnvBq
answer:
DtWLln


question:
wkVVZREWhcSCpvCTB, ZQWhcSCpvCDVUY
answer:
WhcSCpvC


question:
LBobZNvIbyyCzcus, qoHZNvIbyyCzcGHiHvPxv
answer:

ZNvIbyyCzc