Weighted shortest path (5) P68936

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.