#include <bits/stdc++.h>
using namespace std;
using ll = long long;

void solve() {
    int n, m;
    cin >> n >> m;
    const ll INF = 1e18;
    vector<vector<pair<int, ll>>> adj(n + 1); // Adjacency list: (neighbor, stench change)

    for (int i = 0; i < m; ++i) {
        int u, v;
        ll s;
        cin >> u >> v >> s;
        adj[u].emplace_back(v, s);
    }

    vector<ll> stench(n + 1, INF);
    vector<bool> in_queue(n + 1, false);
    vector<int> cnt(n + 1, 0); // Count of relaxations for negative cycle detection (not needed here)
    stench[1] = 0;
    queue<int> q;
    q.push(1);
    in_queue[1] = true;

    while (!q.empty()) {
        int u = q.front();
        q.pop();
        in_queue[u] = false;

        for (auto &[v, s_uv] : adj[u]) {
            ll s_v_candidate = max(0LL, stench[u] + s_uv);
            if (s_v_candidate < stench[v]) {
                stench[v] = s_v_candidate;
                if (!in_queue[v]) {
                    q.push(v);
                    in_queue[v] = true;
                    // cnt[v]++;
                    // Optional negative cycle detection, but not necessary here
                }
            }
        }
    }

    cout << stench[n] << '\n';
}


int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();

    return 0;
}