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

const int iinf = 1e9;
const ll inf = 1e18;

template<typename T>
ostream& operator<<(ostream &o, vector<T> v) {
    for (int i = 0; i < v.size(); i++)
        o << v[i] << (i+1<v.size()?" ":"");
    return o;
}

struct Edge { int to; ll cost; };

int main() {
    cin.tie(0)->sync_with_stdio(false);

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

    vector<int> parent(N+1, 0), order;
    order.reserve(N);
    stack<int> st;
    st.push(1);
    parent[1] = -1;
    while(!st.empty()){
        int u = st.top(); st.pop();
        order.push_back(u);
        for(auto [v,w]: adj[u]){
            if(parent[v] == 0){
                parent[v] = u;
                st.push(v);
            }
        }
    }

    vector<ll> bestDown(N+1, 0);
    ll ans = 0;
    for(int idx = N-1; idx >= 0; idx--){
        int u = order[idx];
        vector<ll> cand;
        cand.reserve(adj[u].size());
        for(auto [v,w]: adj[u]){
            if(parent[v] == u){
                cand.push_back(bestDown[v] + w);
            }
        }
        ll mx = 0;
        for(ll x : cand) if(x > mx) mx = x;
        bestDown[u] = mx;

        ll x = 0, y = 0;
        for(ll v : cand){
            if(v > x){ y = x; x = v; }
            else if(v > y){ y = v; }
        }
        ans = max(ans, x + y);
    }

    if(ans > 0) cout << ans << "\n";
    else        cout << 0 << "\n";
    return 0;
}