#include <bits/stdc++.h>
using namespace std;
 
#define int long long
#define pi pair<int,int>
#define nn '\n'
 
const int N = 200000 + 5;
const int K = 30;               // log2(1e9) < 30
const long long NEG = -1e18;
 
int n, m;
vector<pi> adj[N];
vector<vector<long long>> dp;
 
int32_t main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y, w;
        cin >> x >> y >> w;
        adj[x].push_back({y, w});
    }
 
    dp.assign(n + 1, vector<long long>(K + 1, NEG));
 
    // (profit, node, steps)
    priority_queue<tuple<long long,int,int>> pq;
 
    dp[1][0] = 0;
    pq.push({0, 1, 0});
 
    while (!pq.empty()) {
        auto [profit, u, k] = pq.top();
        pq.pop();
 
        if (profit < dp[u][k]) continue;
 
        for (auto [v, w] : adj[u]) {
            if (k + 1 > K) continue;
 
            long long gain = w >> k;
            if (gain == 0) continue;
 
            if (dp[v][k + 1] < profit + gain) {
                dp[v][k + 1] = profit + gain;
                pq.push({dp[v][k + 1], v, k + 1});
            }
        }
    }
 
    long long ans = 0;
    for (int u = 1; u <= n; u++)
        for (int k = 0; k <= K; k++)
            ans = max(ans, dp[u][k]);
 
    cout << ans << nn;
    return 0;
}
 

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