#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

typedef long long ll;

struct Edge {
    int to;
    ll weight;
};

vector<vector<Edge>> adj;
ll ans = 0;

ll dfs(int u, int p) {
    ll max1 = 0;
    ll max2 = 0;

    for (const auto& edge : adj[u]) {
        int v = edge.to;
        ll w = edge.weight;
        if (v == p) continue;

        ll path_from_v_subtree = dfs(v, u);

        ll current_path_through_v = 0;
        if (path_from_v_subtree + w > 0) {
            current_path_through_v = path_from_v_subtree + w;
        }

        if (current_path_through_v >= max1) {
            max2 = max1;
            max1 = current_path_through_v;
        } else if (current_path_through_v > max2) {
            max2 = current_path_through_v;
        }
    }

    ans = max(ans, max1 + max2);

    return max1;
}


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n;
    cin >> n;

    adj.resize(n);
    for (int i = 0; i < n - 1; ++i) {
        int u_node, v_node;
        ll w;
        cin >> u_node >> v_node >> w;
        --u_node; --v_node;
        adj[u_node].push_back({v_node, w});
        adj[v_node].push_back({u_node, w});
    }

    if (n == 1) {
         cout << 0 << endl;
         return 0;
    }

    dfs(0, -1);

    cout << ans << endl;

    return 0;
}