#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int read(){
	int x =0 ;char c= getchar();
	while(c<'0' or c>'9')c = getchar();
	while('0'<=c and c<='9'){
		x = x*10+(c^48),c =getchar();
	}return x;
}int n;
int fa[500005],sz[500005];
int now =0,ans =0 ;
vector<int>lf;
inline int find(int x){
	if(x == fa[x])return x;
	return find(fa[x]);
}void merge(int a,int b){
	int x=  find(a),y = find(b);
	if(x == y)return;
	if(sz[x]>sz[y])swap(x,y);
	fa[x] = y;
	now+=sz[y]*sz[x];
	sz[y]+=sz[x];
	lf.push_back(x);return;
}inline void del(){
	if(lf.empty())return;
	int x = lf.back();lf.pop_back();
	int tt = fa[x];
	sz[fa[x]]-=sz[x],fa[x] = x;
	now-=sz[tt]*sz[x];
	return;
}struct node{
	int l,r;
	vector<pair<int,int> >q;
}tree[2000005];
inline void build(int k,int l,int r){
	tree[k].l = l,tree[k].r = r;
	if(l+1 == r)return;
	build(k<<1,l,l+r>>1),build(k<<1|1,l+r>>1,r);
}inline void upd(int k,int l,int r,int x,int y){
	int ll = tree[k].l,rr = tree[k].r;
	if(l>=rr or ll>=r)return;
	if(l<=ll and rr<=r){
		tree[k].q.push_back({x,y});return;
	}upd(k<<1,l,r,x,y),upd(k<<1|1,l,r,x,y);
	return;
}inline void dfs(int k){
	int l = tree[k].l,r = tree[k].r,o = lf.size();
	//cout << l << " " << r << endl;
	for(int i =0;i<tree[k].q.size();i++){
	//	cout << " " << tree[k].q[i].first << " " << tree[k].q[i].second << endl;
		merge(tree[k].q[i].first,tree[k].q[i].second);
	}if(l+1 == r){
	//	cout << l << " "<< now << endl;
		ans+=n*(n-1)/2-now;
	}else dfs(k<<1),dfs(k<<1|1);
	while(lf.size()>o)del();return;
}
signed main(){
	n = read();
	for(int i = 1;i<=n;i++)fa[i] = i,sz[i] = 1;
	build(1,1,n+1);
	for(int i = 1;i<n;i++){
		int a = read(),b = read(),c = read();
		if(c!=1)upd(1,1,c,a,b);
		if(c!=n)upd(1,c+1,n+1,a,b);
	}dfs(1);
	cout << ans*2 << endl;
	return 0;
}