#include <bits/stdc++.h>
#define be(v) (v).begin(),(v).end()
#define pb(q) push_back(q)
typedef long long ll;
using namespace std;
const ll mod=1000000007, INF=(1LL<<60);
#define doublecout(a) cout<<fixed<<setprecision(10)<<a<<endl;

ll calc(ll x, ll y){return x*x + y*y;}
int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(false);
    ll n, a, b;
    cin >> n;
    bool burst[n];
    memset(burst, 0, sizeof(burst));
    vector<pair<ll, ll> > v;
    multiset<pair<ll, pair<int, int> > > ms;
    for(int i=0;i<n;i++){
    	cin >> a >> b;
    	v.push_back({a, b});
    }
    for(int i=0;i<n;i++){
    	for(int j=0;j<n;j++){
    		if(i == j) continue;
    		ms.insert({calc(v[i].first - v[j].first, v[i].second - v[j].second), {i, j}});
    	}
    }
    int ans = 0;
    while(!ms.empty()){

    	auto itr = ms.begin();
    	int id1 = itr->second.first;
    	int id2 = itr->second.second;
    	ms.erase(itr);
    	if(burst[id1] || burst[id2]) continue;
    	if(id1 > id2) swap(id1, id2);
    	if(id1 == 0){
    		burst[id2] = true;
    		ans++;
    	}else{
    		burst[id1] = burst[id2] = true;
    	}
    }
    cout << ans << endl;
    return 0;
}