#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
    int n;cin>>n;
    vector<vector<pair<int,int>>>connect(n);
    for(int i=0;i<n-1;i++){
        int a,b,c;cin>>a>>b>>c;
        a--;b--;
        connect[a].push_back({b,c});
        connect[b].push_back({a,c});
    }
    //関数の返り値->遠い奴のコストも一緒に
    const int inf=1e18;
    auto BFS=[&](auto BFS,int start)->pair<int,int>{
        vector<bool>vis(n,false);
        vector<int>dist(n,inf);
        dist[start]=0;
        vis[start]=true;
        deque<int>que;
        que.push_back(start);
        while(!que.empty()){
            int now=que.front();
            que.pop_front();
            for(auto [to,weight]:connect[now]){
                if(!vis[to]){
                    vis[to]=true;
                    dist[to]=dist[now]+weight;
                    que.push_back(to);
                }
            }
        }
        int o=0,t=0;
        for(int i=0;i<n;i++){
            if(dist[i]>t){
                t=dist[i];
                o=i;
            }
        }
        return {o,t};
    };
    auto[nxt,w]=BFS(BFS,0);
    auto[d,ans]=BFS(BFS,nxt);
    cout<<ans<<endl;
}