#include<iostream>
#include<vector>
#include <queue>
#define INF 32000
using namespace std;

vector < vector< pair<long long, long long> > > graph;

long long n, m, x, y, z;

void dijkstra(int s){
    vector<long long> d(n+1, INF);
    d[s]=0;
    priority_queue <pair<int, int> > q;
    q.push(make_pair(s, 0));
    while(!q.empty()){
        pair<int, int> top = q.top();
        q.pop();
        for(int i=0; i<graph[top.first].size(); i++){
            int cur_vert=graph[top.first][i].first;
            int cur_dist = graph[top.first][i].second;
            if(d[cur_vert]>d[top.first]+cur_dist){
                d[cur_vert]=d[top.first]+cur_dist;
                q.push(make_pair(cur_vert, d[top.first]+cur_dist));
            }
        }
    }

    if(d[n]==INF) cout<<-1<<endl;
    else cout<<d[n]<<endl;
}

int main()
{
    cin>>n>>m;
    graph.resize(n+1);
    for(int i=0; i<m; i++){
        cin>>x>>y>>z;
        graph[x].push_back(make_pair(y, z));
    }
    dijkstra(1);


    return 0;
}