#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i=0; i<n; i++)
#define pb push_back
#define int long long
typedef tuple<int, int, int> T;

bool flag[1010];

signed main() {
    cin.tie(0); ios::sync_with_stdio(false);
    int N; cin >> N;
    int x[N], y[N];
    rep(i, N) cin >> x[i] >> y[i];
    vector<T> l;
    rep(i, N) for (int j=i+1; j<N; j++) {
        l.push_back(make_tuple((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]), i, j));
    }
    sort(l.begin(), l.end());
    int ans = 0;
    for (int i=0; i<l.size(); i++) {
        int j = get<1>(l[i]), k = get<2>(l[i]);
        if (flag[j] || flag[k]) continue;
        if (j==0) {
            ans++;
            flag[k] = true;
        }
        else if (k==0) {
            ans++;
            flag[j] = true;
        }
        else {
            flag[j] = true;
            flag[k] = true;
        }
    }
    cout << ans << endl;
}