CSES 1673 High Score - The Maximum-Score Trick

Maximum score equals the minimum of negated scores. Negate all edge weights and run shortest-path algorithms.

This converts the problem into finding the shortest path with negated weights. If a negative cycle exists and affects the path, the answer is $-1$ (infinite score).

Use Bellman-Ford to detect negative cycles after negation. Run $N-1$ relaxation rounds, then check if a $N$-th round still relaxes any edge reachable from $1$ that can reach $N$. If so, output $-1$.