#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    int n; cin >> n;
    ll x[n], y[n];
    rep(i,n) cin >> x[i] >> y[i];
    vector<pair<ll,P>> v;

    /*
    ll d[n][n];
    rep(i,n){
        rep(j,n){
            d[i][j] = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
            cout << d[i][j] << ' ';
        }
        cout << endl;
    }
    */

    rep(i,n){
        srep(j,i+1,n){
            pair<ll,P> p;
            p.first = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
            p.second.first = i;
            p.second.second = j;
            v.push_back(p);
        }
    }

    sort(v.begin(), v.end());

    int f[n] = {};
    int ans = 0;
    rep(i,v.size()){
        if(v[i].second.first == 0){
            if(f[v[i].second.second] == 0){
                ans++;
                f[v[i].second.second] = 1;
            }
        }else{
            if(f[v[i].second.first] == 0 && f[v[i].second.second] == 0){
                f[v[i].second.first] = 1;
                f[v[i].second.second] = 1;
            }
        }
    }

    cout << ans << endl;
    return 0;
}