instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
RMurrwPjlfG, QBKrrwPDkTM
answer:
rrwP


question:
kWTQrtCaoTbXIiXDphMG, pLhxkfeDoTbXIiXDpCCzTYyZv
answer:
oTbXIiXDp


question:
uPupdePuy, oABTiupdePDEsB
answer:

updeP