#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
const int N = 1500 + 10;
int n, m, a, b, w;
vector<int> G[N], c[N];
bool l[N]; int f[N];
int Dijkstra(int s, int t) {
    priority_queue<pair<int, int> > q;
    memset(l, 0, sizeof(l));
    memset(f, -1, sizeof(f));
    q.push(make_pair(f[s] = 0, s));
    while(!q.empty()) {
        int u = q.top().second; q.pop();
        if(!l[u]) {
            l[u] = 1;
            for(int i=0; i<G[u].size(); i++) {
                int v = G[u][i];
                if(!l[v] && f[v] < f[u] + c[u][i]) {
                    f[v] = f[u] + c[u][i];
                    q.push(make_pair(f[v], v));
                }
            }
        }
    } return f[t];
}
int Bellman(int s, int t) {
    queue<int> q;
    memset(l, 0, sizeof(l));
    memset(f, -1, sizeof(f));
    f[s] = 0; q.push(s);
    while(!q.empty()) {
        int u = q.front(); q.pop();
        l[u] = 0;
        for(int i=0; i<G[u].size(); i++) {
            int v = G[u][i];
            if(!l[v] && f[v] < f[u] + c[u][i]) {
                f[v] = f[u] + c[u][i];
                q.push(v);
            }
        }
    } return f[t];
}
int main() {
    freopen("longest.in", "r", stdin);
    freopen("longest.out", "w", stdout);
    scanf("%d %d", &n, &m);
    for(int i=0; i<m; i++) {
        scanf("%d %d %d", &a, &b, &w);
        G[a].push_back(b);
        c[a].push_back(w);
    }
    //printf("%d\n", Dijkstra(1, n));
    printf("%d\n", Bellman(1, n));
    return 0;
}