#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,ans;
struct node{
    int v,w;
};
vector<node> g[1000009];
int sz[1000009];
void dfs(int u,int fa){
    sz[u] = 1;
    for(auto [v,w]:g[u]){
        if(v == fa) continue;
        dfs(v,u);
        sz[u]+=sz[v];
        ans+=abs(sz[v]-(n-sz[v]))*w;
    }
}
signed main(){
    cin>>n;
    for(int i = 1;i<n;++i){
        int u,v,w;
        cin>>u>>v>>w;
        g[u].push_back({v,w});
        g[v].push_back({u,w});
    }
    dfs(1,0);
    cout<<ans;
}