Weighted shortest path (5)

Write a program that, given a directed graph with postive and/or negative costs at the arcs (but no negative cycles), and two vertices $x$ and $y$ , computes the minimum cost to go from $x$ to $y$ .

Input

Input consists of several cases. Every case begins with the number of vertices $n$ and the number of arcs $m$ . Follow $m$ triples $u, v, c$ , indicating that there is an arc $u \to v$ of cost $c$ , where $u \ne v$ , $-1000 \le c \le 1000$ and $c\neq 0$ . Finally, we have $x$ and $y$ . Assume $1 \le n \le 10^4$ , $0 \le m \le 5n$ , and that for every pair of vertices $u$ and $v$ there is at most one arc of the kind $u \to v$ . All numbers are integers. Vertices are numbered from 0 to $n-1$ . The directed graph has no negative cycles.

Output

For every case, print the minimum cost to go from $x$ to $y$ , if this is possible. If there is no path from $x$ to $y$ , state so.

Problem information

Author: Jordi Petit

Generation: 2026-01-25T11:37:36.868Z