#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll maxn = 1e5 + 5;
ll n, dp[maxn], sz[maxn];
vector<pair<ll, ll> >edge[maxn];
inline ll read(){
ll s = 0, w = 1; char ch = getchar();
while(ch < '0' || ch > '9'){ if(ch == '-') w = -1; ch = getchar();}
while(ch >= '0' && ch <= '9') s = s * 10 + ch - '0', ch = getchar();
return s * w;
}
inline void print(ll x){
if(x < 0) x = ~x + 1, putchar('-');
if(x > 9) print(x / 10);
putchar(x % 10 + '0');
}
void dfs(ll u, ll f){
sz[u] = 1;
for(auto i : edge[u]){
ll v = i.first, w = i.second;
if(v == f) continue;
dfs(v, u);
sz[u] += sz[v];
dp[u] += (dp[v] + sz[v] * (n - sz[v]) * w);
}
}
int main(){
n = read();
for(int i = 1; i < n; i++){
ll u = read(), v = read(), w = read();
edge[u].push_back(make_pair(v, w));
edge[v].push_back(make_pair(u, w));
}
dfs(1, 0);
print(dp[1]);
return 0;
} 
