#include <cstdio>
#include <algorithm>
typedef long long ll;

int n;
ll num[20005],fa[20005],ans; //num用来统计联通快的数量
struct node{
    ll u,v,w;
}e[20005];

bool CMP(const node &a,const node&b){
    return a.w<b.w;
}

ll find(int x){
    if(x!=fa[x]) fa[x] = find(fa[x]);
    return fa[x];
}

void merge(int x,int y,int z){
    x = find(x);
    y = find(y);
    ans += (num[x]*num[y]-1) * (z+1);   //这里是核心
    fa[y]=x;
    num[x]+=num[y];
}

void Run(){
    for(int i=1;i<=n;i++){
        fa[i]=i;
        num[i]=1;
    }
    for(int i=1;i<n;i++){
        ans+=e[i].w; //加上两点的边
        merge(e[i].u,e[i].v,e[i].w);
    }
}

void init(){
    scanf("%d",&n);
    for(int i=1;i<n;i++){
        scanf("%lld%lld%lld",&e[i].u,&e[i].v,&e[i].w);
    }
    std::sort(e+1,e+n,CMP);
}

int main(){
    init();    
    Run();
    printf("%lld\n",ans);
    return 0;
}