Town Judge - The Story

There are $N$ people. There is a rumor of a secret judge. Rules:

$1.$ The town judge trusts nobody.

$2.$ Everybody (except the judge) trusts the judge.

$3.$ Exactly one person satisfies both conditions.

In graph terms: the judge has in-degree $N-1$ and out-degree $0$. You do not need to build an actual graph. Count degrees. For each trust pair $(a, b)$, increment $bs in-degree and$as out-degree. Find the person matching both conditions. If none exists, return $-1$.