instruction:
In this task, you are given two strings A, B. Find the longest common substring in the strings A and B.
question:
EJZYVxgFxPoOSDlLfK, uTLTIETHZYVxgFxPoPwr
answer:
ZYVxgFxPo


question:
fVEFJa, WtEFYK
answer:
EF


question:
RnvHQFdQwDEqLvkqjGYaVSiie, VEncfBSvCSFdQwDEqLvkpUPXagYMH
answer:

FdQwDEqLvk