2022 SSMO Accuracy Round Problems/Problem 9

Problem

The graph $\Gamma$ has $52$ vertices labeled $A, A', B, B', \dots, Z, Z'$, such that $A$ is not connected to $A'$, $B$ is not connected to $B'$, and so on. Suppose that all the vertices other than $A'$ have different degrees (number of connections to the vertex). Find the sum of all possible values for the number of edges (connections) in $\Gamma$.

Solution