Example

Input

5
1 2
1 3
1 4
1 5


Output

6
#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
using namespace std;
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
typedef long double ld;
typedef complex<ld> Point;
const ll INF = mod * mod;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
const ld eps = 1e-6;
const ld pi = acos(-1.0);
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;

vector<int> G[1 << 17];

const ll t = 999999937;
const ll m = mod+2;

vector<ll> h;

void dfs(int v, int fr) {
	h[v] = 0;
	rep(j, G[v].size()) {
		int to = G[v][j];
		if (to == fr)continue;
		dfs(to, v);
		h[v] += h[to];
		if (h[v] >= m)h[v] -= m;
	}
	h[v] = (h[v] * t+1)%m;
}

void solve() {
	int n; cin >> n;
	rep(i, n - 1) {
		int a, b; cin >> a >> b; a--; b--;
		G[a].push_back(b);
		G[b].push_back(a);
	}
	h.resize(n);
	dfs(0, -1);
	sort(h.begin(), h.end());
	ll ans = 0;
	rep(i, h.size()) {
		int le = i;
		while (i + 1 < n&&h[i + 1] == h[i])i++;
		ll len = i - le + 1;
		ans += len * (len - 1) / 2;
	}
	cout << ans << endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	solve();
	//stop
	return 0;
}
