#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
	priority_queue<tuple<ll,int,int>,vector<tuple<ll,int,int>>,greater<tuple<ll,int,int>>> que;

	int N;
	cin >> N;
	vector<ll> x(N);
	vector<ll> y(N);
	for(int i = 0;i < N;i++){
		cin >> x[i] >> y[i];
	}

	for(int i = 0;i < N-1;i++){
		for(int j = i+1;j < N;j++){
			ll x1 = x[i];
			ll x2 = x[j];
			ll y1 = y[i];
			ll y2 = y[j];
			que.push(make_tuple((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2),i,j));
		}
	}

	vector<bool> used(N,false);
	int cnt = 0;
	while(que.size()){
		ll d,i,j;
		tie(d,i,j) = que.top();
		que.pop();
		if(used[i] || used[j])continue;
		if(i == 0 || j == 0){
			cnt++;
			used[max(i,j)] = true;
		}
		else used[i] = used[j] = true;
	}

	cout << cnt << endl;
}