#include <bits/stdc++.h>
using namespace std;
int g[1510][1510];
int ans[1510];
int main(){
    memset(ans,-1,6040);
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=m;i++){  
        int u,v,x;
        cin>>u>>v>>x;
        g[u][v] = x;
    }
    ans[1] = 0;
    queue<int> q;
    q.push(1);
    while(q.size()){
        int t = q.front();
        q.pop();
        for(int i=1;i<=n;i++){
            int tmp = ans[i];
            if(!g[t][i]) continue;
            ans[i] = max(ans[i],ans[t]+g[t][i]);
            if(ans[i]!=tmp) q.push(i);
        }
    }
    cout<<ans[n];
    system("pause");
    return 0;
}