Combinatorics Harvard-MIT
2017


Problem - 4507

There are $2017$ frogs and $2017$ toads in a room. Each frog is friends with exactly $2$ distinct toads. Let $N$ be the number of ways to pair every frog with a toad who is its friend, so that no toad is paired with more than one frog. Let $D$ be the number of distinct possible values of $N$, and let $S$ be the sum of all possible values of $N$. Find the ordered pair $(D,\ S)$.


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