#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N=1e5+10;
struct node{int x, y, c;} a[N];
bool cmp(node n1, node n2) {return n1.c < n2.c;}
int f[N], s[N];
int findfa(int x) {return (f[x]==x)? f[x]: f[x]=findfa(f[x]);}
int main()
{
    int n; scanf("%d", &n);
    for(int i=1; i<=n; i++) f[i]=i, s[i]=1;
    for(int i=1; i<n; i++)scanf("%d%d%d", &a[i].x, &a[i].y, &a[i].c);
    sort(a+1, a+n, cmp);
    LL ans=0;
    for(int i=1; i<n; i++)
    {
        int x=a[i].x, y=a[i].y;
        int tx=findfa(x), ty=findfa(y);
        ans=ans+(LL)(s[tx]*s[ty]-1)*(a[i].c+1)+a[i].c;
        f[tx]=ty; s[ty]+=s[tx];
    }
    printf("%lld\n", ans);
    return 0;
}