include

include

include

using namespace std;

define INF 0x3f3f3f3f

define N 20005

int fa[N], Size[N], n;

struct node {

int u, v, w;

} e[N];

bool cmp(node &a, node &b) {

return a.w < b.w;

}

void init() {

for (int i = 0; i <= n; i++) {
	fa[i] = i;
	Size[i] = 1;
}

}

int find(int i) {

if (i == fa[i])
	return i;
else {
	fa[i] = find(fa[i]);
	return fa[i];
}

}

void unionn(int i, int j) {

int ifa = find(i);
int jfa = find(j);
fa[jfa] = ifa;

}

void kruskal() {

sort(e, e + n - 1, cmp);
int res = 0;
for (int i = 0; i < n - 1; i++) {
	int a = find(e[i].u), b = find(e[i].v), w = e[i].w;
	if (a != b) {
		res += (Size[a] * Size[b] - 1) * (w + 1);
		fa[a] = b;
		Size[b] += Size[a];
	}
}
cout << res << endl;

}

int main() {

cin >> n;
for (int i = 0; i < n - 1; i++) {
	cin >> e[i].u >> e[i].v >> e[i].w;
}
init();
kruskal();
return 0;

}