#include<bits/stdc++.h>
#define int long long
using namespace std;
int dist(int A,int B){return A*A+B*B;}
int X[1100],Y[1100];
signed main(){
    int N;
    cin>>N;
    for(int i=0;i<N;i++)cin>>X[i]>>Y[i];
    vector<pair<int,int>> A;
    for(int i=0;i<N;i++){
        for(int j=i+1;j<N;j++)A.push_back({dist(X[i]-X[j],Y[i]-Y[j]),i*N+j});
    }
    sort(A.begin(),A.end());
    vector<int> B(N,0);
    B[0]=0;
    for(auto p:A){
        int a=p.second/N,b=p.second%N;
        if(B[a]+B[b]>=1)continue;
        else if(B[a]==-1)B[b]=-1;
        else if(B[b]==-1)B[a]=-1;
        else B[a]=B[b]=1;
    }
    int ans=0;
    for(int i=1;i<N;i++){
        if(B[i]==-1)ans++;
    }
    cout<<ans<<endl;
}