#include <bits/stdc++.h>

using namespace std;

bool check[1001];

int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n;
    vector <pair<int,int>> v;
    int x,y;

    cin >> n;

    for(int i=0;i<n;i++)
    {
        cin >> x >> y;
        v.push_back(make_pair(x,y));
    }

    vector <pair<long long int,pair<int,int>>> vec;

    for(int i=0;i<n;i++)
    {
        for(int j=i+1;j<n;j++)
        {
            long long int dy = v[j].first - v[i].first;
            long long int dx = v[j].second - v[i].second;
            long long int D = dy*dy + dx*dx;
            vec.push_back(make_pair(D,make_pair(i,j)));
        }
    }

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

    int res = 0;

    for(int i=0;i<vec.size();i++)
    {
        int u = vec[i].second.first;
        int v = vec[i].second.second;
        if(check[u] || check[v]) continue;
        if(u==0)
        {
            res++;
            check[v] = true;
        }
        else if(v==0)
        {
            res++;
            check[u] = true;
        }
        else
        {
            check[u] = true;
            check[v] = true;
        }
    }

    cout << res << '\n';

    return 0;
}