#include<bits/stdc++.h>
//#include<atcoder/all>
using namespace std;
//using namespace atcoder;
#define fs first
#define sc second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
#define RALL(A) A.rbegin(),A.rend()
typedef long long ll;
typedef pair<ll,ll> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
const ll mod=1000000007;
const ll LINF=1ll<<60;
const int INF=1<<30;
int dx[]={1,0,-1,0,1,-1,1,-1};
int dy[]={0,1,0,-1,1,-1,-1,1};




int main(){
    int n;cin >> n;
    vector<int> x(n), y(n);
    for (int i = 0; i < n; i++) {
        cin >> x[i] >> y[i];
    }
    vector<pair<ll, P>> v;
    for (int i = 0; i < n; i++) {
        for (int j = i + 1; j < n; j++) {
            ll X = x[i] - x[j], Y = y[i] - y[j];
            v.pb(mp(X*X+Y*Y, mp(i, j)));
        }
    }
    sort(ALL(v));
    int ans = 0;
    vector<bool> used(n, false);
    for (int i = 0; i < v.size(); i++) {
        if(used[v[i].sc.fs] or used[v[i].sc.sc]) continue;
        if(v[i].sc.fs == 0){
            ans++;
            used[v[i].sc.sc] = true;
        }
        else{
            used[v[i].sc.fs] = true;
            used[v[i].sc.sc] = true;
        }
    }
    cout << ans << endl;
    return 0;
}