//
// Created by yamunaku on 2020/10/23.
//

#include <bits/stdc++.h>
//#include <atcoder/all>

using namespace std;
//using namespace atcoder;

#define rep(i, n) for(int i = 0; i < (n); i++)
#define repl(i, l, r) for(int i = (l); i < (r); i++)
#define per(i, n) for(int i = ((n)-1); i >= 0; i--)
#define perl(i, l, r) for(int i = ((r)-1); i >= (l); i--)
#define all(x) (x).begin(),(x).end()
#define MOD9 998244353
#define MOD1 1000000007
#define IINF 1000000000
#define LINF 1000000000000000000
#define SP <<" "<<
#define CYES cout<<"Yes"<<endl
#define CNO cout<<"No"<<endl
#define CFS cin.tie(0);ios::sync_with_stdio(false)
#define CST(x) cout<<fixed<<setprecision(x)

using ll = long long;
using ld = long double;
using vi = vector<int>;
using mti = vector<vector<int>>;
using vl = vector<ll>;
using mtl = vector<vector<ll>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
template<typename T>
using heap = priority_queue<T, vector<T>, function<bool(const T, const T)>>;

int main() {
    //CFS;
    int n;
    cin >> n;
    vl x(n), y(n);
    rep(i, n) {
        cin >> x[i] >> y[i];
    }
    vector<pair<ll, pair<int, int>>> v;
    rep(i, n) {
        repl(j, i + 1, n) {
            v.push_back({(x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]), {i, j}});
        }
    }
    sort(all(v));
    vi used(n, false);
    int ans = 0;
    for (auto &p : v) {
        if (used[p.second.first] || used[p.second.second]) continue;
        if (p.second.first == 0) {
            ans++;
            used[p.second.second] = true;
            continue;
        }
        used[p.second.first] = used[p.second.second] = true;
    }
    cout << ans << endl;
    return 0;
}