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MathNet 2026 — Part 05 Question 64

Math Olympiad Vault · MathNet 2026 — Part 05

Question 64

There are $100$ towns on the island of Hibernia. Every pair of towns is either connected by a single road, or is not connected. If we consider any subset of $98$ towns, the total number of roads connecting these towns to each other is a constant. There are $N$ roads in total in Hibernia.
Find all possible values of $N$.