#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define rrep(i,n) for (int i = (n)-1; i >= 0; --i)
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
using namespace std;
using ll = long long;
using P = pair<int,int>;
using VI = vector<ll>;
using VVI = vector<VI>;

ll d2(ll dx, ll dy) {return dx * dx + dy * dy;}

int main() {
    int n;
    cin >> n;
    VI x(n), y(n);
    rep(i, n) cin >> x[i] >> y[i];
    priority_queue<
        tuple<ll,int,int>,
        vector<tuple<ll,int,int>>,
        greater<tuple<ll,int,int>>> q;
    rep(i, n) rep(j, i) {
        // j < i
        q.emplace(d2(x[i]-x[j], y[i]-y[j]), i, j);
    }
    int ans = 0;
    vector<bool> alive(n, true);
    while(!q.empty()) {
        ll d;
        int i, j;
        tie(d, i, j) = q.top(); q.pop();
        if (j == 0) {
            if (alive[i]) {
                ++ans;
                alive[i] = false;
            }
        } else {
            if (alive[i] && alive[j]) {
                alive[i] = alive[j] = false;
            }
        }
    }
    cout << ans << endl;
}