No Unpaired Chefs

Codechef has now decided to make an admin panel amongst their chefs. This way they think that it would be easier for them to control and regulate their contests. To do so, they have asked them to rate everyone including themselves by a non-negative integer. There are N chefs, numbered from 1 to N. Each chef has submitted a rating to the Codechef panel for other all the chefs including a rating t