#include<bits/stdc++.h>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
int n,u,v,w,k,sum;
struct edge{int x,y;};
vector<edge> a[200001];
int bfs(int s){
	int maxn = s;
	int tr[100002];
	memset(tr, 0 ,sizeof(tr));
	tr[s] = 1;
    queue<int> q;
    q.push(s);
    while(!q.empty()){
        int l = q.front();
        q.pop();
        for(int i = 0;i < a[l].size();i++){
            if(tr[a[l][i].x] == 0){
                q.push(a[l][i].x);
                tr[a[l][i].x] = tr[l] + a[l][i].y;
                if(tr[maxn] < tr[a[l][i].x]){
                	maxn = a[l][i].x;
				}
            }
        }
    }
    sum = tr[maxn] - 1;
    return maxn;
}
int main(){
    scanf("%d",&n);
    k = n;
    while(--n){
        scanf("%d%d%d",&u,&v,&w);
        a[u].push_back({v,w});
        a[v].push_back({u,w});
    }
    bfs(bfs(1));
    printf("%d",sum);
    return 0;
}

两次bfs就可以了，easy