#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);
    stench[1] = 0;
    // Priority queue: (stench level, node)
    priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<>> pq;
    pq.emplace(0, 1);
    
    while (!pq.empty()) {
        auto [s_u, u] = pq.top();
        pq.pop();
        
        // If we have already found a better stench level, skip
        if (s_u > stench[u]) continue;
        
        for (auto &[v, s_uv] : adj[u]) {
            ll s_v_candidate = max(0LL, s_u + s_uv);
            if (s_v_candidate < stench[v]) {
                stench[v] = s_v_candidate;
                pq.emplace(stench[v], v);
            }
        }
    }
    
    cout << stench[n] << '\n';
}

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

    solve();

    return 0;
}