#include <iostream>
#include <vector>

using int64 = long long;

template<class T>
class Edge {
public:
    int to;
    T weight;
    Edge(int to, T weight) : to{to}, weight{weight} {}
};

using Graph = std::vector<std::vector<Edge<int64>>>;

int64 ans = 0;

int64 dfs(int v, int par, const Graph& g)
{
    int64 max1 = 0, max2 = 0;
    for (auto& e : g[v]) {
        if (e.to == par) continue;
        int64 val = dfs(e.to, v, g) + e.weight;
        if (val > max1) {
            max2 = max1;
            max1 = val;
        } else if (val > max2) {
            max2 = val;
        }
    }
    ans = std::max(ans, max1 + max2);
    ans = std::max(ans, max1); 
    return std::max<int64>(0, max1);
}

int main()
{
    int N;
    std::cin >> N;
    Graph g(N);
    int64 u, v, w;
    for (int i = 0; i < N - 1; i++) {
        std::cin >> u >> v >> w;
        u--; v--;
        g[u].emplace_back(v, w);
        g[v].emplace_back(u, w);
    }
    dfs(0, -1, g);
    std::cout << ans << std::endl;
    return 0;
}