#include <bits/stdc++.h>
 
using namespace std;
#define all(x) (x).begin(),(x).end()
#define rep(i, n) for (int i = 0; i < (n); i++)
#define chmin(x, y) (x) = min((x), (y))
#define chmax(x, y) (x) = max((x), (y))
#define endl "\n"
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
 
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {os << "["; for (const auto &v : vec) {os << v << ","; } os << "]"; return os;}
template <typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &p) {os << "(" << p.first << ", " << p.second << ")"; return os;}
 
struct D {
    ll d, s, t;
    bool operator<(const D& rhs) const {
        return d < rhs.d;
    }
    bool operator>(const D& rhs) const {
        return d > rhs.d;
    }
};

void solve() {
    int N;
    cin >> N;
    vector<pii> A(N);
    for (int i = 0; i < N; i++) {
        ll a, b;
        cin >> a >> b;
        A[i] = {a, b};
    }

    priority_queue<D, vector<D>, greater<D>> Ds;
    for (int i = 0; i < N; i++) {
        for (int j = i + 1; j < N; j++) {
            ll d = (A[i].first - A[j].first) * (A[i].first - A[j].first) + (A[i].second - A[j].second) * (A[i].second - A[j].second);
            Ds.push((D){d, i, j});
        }
    }

    vector<int> alive(N, 1);
    int ans = 0;
    while(!Ds.empty()) {
        D d = Ds.top(); Ds.pop();
        if (!alive[d.s] || !alive[d.t]) continue;
        if (d.s == 0) {
            alive[d.t] = 0;
            ans++;
        } else {
            alive[d.s] = alive[d.t] = 0;
        }
    }

    cout << ans << endl;
}

int main() {
    #ifdef LOCAL_ENV
    cin.exceptions(ios::failbit);
    #endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout.setf(ios::fixed);
    cout.precision(16);
    
    solve();
}