#include<bits/stdc++.h>

using namespace std;
using ll = long long;


int main()
{
    int N; cin >> N;
    vector<ll> x(N), y(N);
    vector<tuple<ll, int, int>> dists;
    for(int i = 0; i < N; i++)cin >> x[i] >> y[i];

    for(int i = 0; i < N; i++) {
        for(int j = i + 1; j < N; j++) {
            dists.emplace_back((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]), i, j);
        }
    }
    sort(dists.begin(), dists.end());
    vector<bool> remain(N);
    int cnt = 0;

    for(auto [dist, i, j] : dists) {
        if(remain[i] || remain[j])continue;
        if(i && j)remain[i] = remain[j] = true;
        else {
            cnt++;
            remain[j] = true;
        }
    }
    cout << cnt << endl;


}