#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
using ll=long long;
typedef pair<int, int> P;

int main()
{
    int n; cin>>n;
    ll x[1010], y[1010];
    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=0; j<i; j++){
            v.push_back({(x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]), {j, i}});
        }
    }
    sort(v.begin(), v.end());
    bool b[2020]={};
    int ans=0;
    for(auto p:v){
        int i=p.second.first, j=p.second.second;
        if(b[i] || b[j]) continue;
        if(i==0){
            ans++;
            b[j]=1;
        }else{
            b[i]=b[j]=1;
        }
    }
    cout<<ans<<endl;
    return 0;
}