#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>
using namespace std;

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

    long long n;
    cin >> n;

    vector<vector<pair<long long, long long>>> graph(n + 1); // 1-indexed

    for (long long i = 0; i < n - 1; ++i) {
        long long u, v, w;
        cin >> u >> v >> w;
        graph[u].emplace_back(v, w);
        graph[v].emplace_back(u, w);
    }

    vector<long long> parent(n + 1, 0);
    vector<long long> order;
    stack<long long> s;
    s.push(1);
    parent[1] = -1;

    while (!s.empty()) {
        long long u = s.top(); s.pop();
        order.push_back(u);
        for (auto [v, w] : graph[u]) {
            if (parent[v] == 0) {
                parent[v] = u;
                s.push(v);
            }
        }
    }

    vector<long long> best_down(n + 1, 0);
    long long answer = 0;

    for (long long i = n - 1; i >= 0; --i) {
        long long u = order[i];
        long long first = 0, second = 0;

        for (auto [v, w] : graph[u]) {
            if (v == parent[u]) continue;
            long long c = best_down[v] + w;
            if (c > first) {
                second = first;
                first = c;
            } else if (c > second) {
                second = c;
            }
        }

        first = max(0LL, first);
        second = max(0LL, second);
        answer = max(answer, first + second);
        best_down[u] = first;
    }

    cout << answer << '\n';
    return 0;
}