#include <bits/stdc++.h>
// #define int long long // 仅在需要大整数时使用，memset 数组为 0x3f 时去掉
#define INF 0x3f3f3f3f
#define PII pair<int, int>
#define ULL unsigned long long
#define PIII tuple<int, int, int>
#define all(v) v.begin(), v.end()
#define debug(a) cout << #a << " = " << a << endl;
using namespace std;
constexpr int N = 1 * 1e5 + 10, M = 2 * 1e5 + 10;

int n, m;
vector<PII> G[M];
int dist[N];
bool st[N]; 
int Dijikstra() {
    memset(dist, 0x3f, sizeof(dist));
    memset(st, false, sizeof(st));
    priority_queue<PII, vector<PII>, greater<PII>> heap;
    heap.push(make_pair(0, 1));
    dist[1] = 0;
    while (heap.size()) {
        auto [d, u] = heap.top();
        heap.pop();
        if (st[u]) continue;
        st[u] = 1;
        for (auto [v, w] : G[u]) {
            if (dist[u] + w < dist[v]) {
                dist[v] = dist[u] + w;
                heap.push(make_pair(dist[v], v));
            }
        }
    }
    return dist[n];
}
void solve() {
    cin >> n >> m;
    for (int i = 0; i < m; i ++) {
        int u, v, w;
        cin >> u >> v >> w;
        G[u].emplace_back(v, w);
    }

    int ans = Dijikstra();
    if (ans >= INF / 2) cout << -1 << '\n';
    else cout << ans << '\n';
}

signed main() {
    ios::sync_with_stdio(0); cin.tie(nullptr), cout.tie(nullptr);
    int _ = 1;
    // cin >> _;
    while (_--) {
        solve();
    }
    return 0;
}

/**
 *    author: Nijika_jia
 *    description: C++17 Algorithm Template for Competitive Programming
 */