srh

///autor: Andrei Margeloiu
# include <bits/stdc++.h>
# define MOD 1000000007
# define NR 100005
# define prim 97
using namespace std;

ifstream f("srh.in");
ofstream g("srh.out");
vector <int> v[NR];
long long key[NR], sol;
int x, y, n;

void DFS (int k, int tata) {
    key[k] = 1;
    for (auto &x: v[k]) {
        if (x != tata) {
            DFS (x, k);
            key[k] += key[x] * prim;
            key[k] %= MOD;
        }
    }
}

int main ()
{
    f>>n;
    for (int i=1; i<n; ++i) {
        f>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }

    DFS(1, 0);
    sort (key+1, key+n+1);
    key[n+1] = -1;
    int i = 1, nr = 1;

    while (i<=n) {
        if (key[i] == key[i+1] && i<=n) {
            while (key[i] == key[i+1]) {
                ++nr;
                ++i;
            }
            sol = sol + 1LL * nr * (nr - 1) / 2;
            nr = 1;
        } else ++i;
    }

    g<<sol<<"\n";

    return 0;
}