#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (ll)(n); i++)
using namespace std;

typedef long long ll;

int main() {
    ll N;
    cin >> N;
    vector<ll> x(N), y(N);
    rep(i, N) cin >> x[i] >> y[i];
    vector<vector<ll>> d;
    for (ll i = 0; i < N - 1; i++) {
        for (ll j = i + 1; j < N; j++) {
            d.push_back({(x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]), i, j});
        }
    }
    sort(d.begin(), d.end());
    vector<bool> done(N, false);
    ll ans = 0;
    rep(i, d.size()) {
        if (done[d[i][1]] || done[d[i][2]]) continue;
        //cout << d[i][1] << " " << d[i][2] << "\n";
        if (d[i][1] == 0) {
            done[d[i][2]] = true;
            ans++;
        } else {
            done[d[i][1]] = true;
            done[d[i][2]] = true;
        }
    }
    cout << ans << "\n";
}