#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;

#define x first
#define y second

signed main(){
	cout<<fixed<<setprecision(10);
	
	int N;
    vector<pair<int,int>> in;
	vector<pair<int,pair<int,int>>> dis;
    vector<int> used;
    int con = 0;
    
    cin>>N;
	
    in.resize(N);
    used.resize(N);
    
    for(int i = 0; i < N; i++){
        cin>>in[i].x>>in[i].y;
    }
    
    for(int i = 0; i < N; i++){
        for(int j = i + 1; j < N; j++){
            dis.push_back({(in[i].x - in[j].x) * (in[i].x - in[j].x) + (in[i].y - in[j].y) * (in[i].y - in[j].y), {i, j}});
        }
    }
    
    sort(dis.begin(), dis.end());
    
    for(int i = 0; i < dis.size(); i++){
        // cout<<dis[i].second.first<<" [] "<<dis[i].second.second<<" "<<dis[i].first<<endl;
        if(used[dis[i].second.first]) continue;
        if(used[dis[i].second.second]) continue;
        // cout<<"<><>"<<endl;
        if(dis[i].second.first == 0) {
            used[dis[i].second.second] = true;
            con++;
            continue;
        }
        
         used[dis[i].second.first] = true;
         used[dis[i].second.second] = true;
    }
    
    cout<<con<<endl;
    
	return 0;
    
}