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

const int MAXN = 500005;

vector<pair<int, ll>> G[MAXN];
ll ans = LLONG_MIN;

ll dfs(int v, int p) {
    ll max1 = 0, max2 = 0;  // 部分木内の最大と2番目のパス長

    for (auto [to, w] : G[v]) {
        if (to == p) continue;
        ll d = dfs(to, v) + w;
        if (d > max1) {
            max2 = max1;
            max1 = d;
        } else if (d > max2) {
            max2 = d;
        }
    }

    ans = max(ans, max1 + max2); // 途中で一番長いパスを更新
    return max1;
}

int main() {
    int N;
    cin >> N;
    for (int i = 0; i < N - 1; ++i) {
        int u, v;
        ll w;
        cin >> u >> v >> w;
        G[u].emplace_back(v, w);
        G[v].emplace_back(u, w);
    }

    dfs(1, -1);
    cout << ans << endl;
    return 0;
}