#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef long long ll;
typedef pair<int, int> P_;
typedef pair<ll, P_> P;

int n;
ll x[1000], y[1000];
bool del[1000];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    cin >> n;
    for(int i = 0; i < n; i++) cin >> x[i] >> y[i];
    vector<P> v;
    for(int i = 0; i < n; i++){
        for(int j = i+1; j < n; j++){
            ll m = (x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]);
            v.push_back(P(m, P_(i, j)));
        }
    }
    sort(v.begin(), v.end());
    int ans = 0;
    for(auto p : v){
        int i = p.second.first;
        int j = p.second.second;
        // cout << i << ' ' << j << endl;
        if(i == 0 && !del[j]){
            ans++;
            del[j] = true;
        }else{
            if((!del[i]) && (!del[j])){
                del[i] = true; del[j] = true;
            }
        }
    }
    cout << ans << endl;
}