using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Diagnostics;
//using nint=System.Int32;
static class Program{
const int mod=(int)1e9+7;
//const double eps=1e-11;
static void Main(){
Sc sc=new Sc();
var n=sc.I;
var h=new long[n][];
var pq=new Pq
>(32,true);
var b=new bool[n+1];
for(int i = 0;i=0;j--) {
pq.Push(((h[i][0]-h[j][0])*(h[i][0]-h[j][0])+(h[i][1]-h[j][1])*(h[i][1]-h[j][1]),(j,i)));
}
b[i]=true;
}
int ans=0;
while(pq.cnt>0){
var e=pq.Top;
pq.Pop();
if(b[e.d.Item1]&&b[e.d.Item2]){
if(e.d.Item1==0){
ans++;
}
else{
b[e.d.Item1]=false;
}
b[e.d.Item2]=false;
}
}
Console.WriteLine("{0}",ans);
}
}
public class Dt:IComparable{
public long n;
public T d;
public static implicit operator Dt((long,T) e){return new Dt(e.Item1,e.Item2);}
public Dt(long n,T d){this.n=n;this.d=d;}
public int CompareTo(object obj){
Dt mymo=(Dt)obj;
if(mymo.n>n){return -1;}
else if(mymo.n"d:"+d.ToString()+" n:"+n.ToString();
}
public class Pq where T:IComparable{
private T[] he;
public int cnt=0,max=0;
private Func compare;
public Pq(int max,bool mm){
this.max=max;
he=new T[max];
if(mm){compare=Ao;}
else{compare=Do;}
}
public void Push(T x){
if(cnt==max){Extend();}
int j=cnt;
while(j!=0&&compare(x,he[(j-1)>>1])>0){he[j]=he[(j-1)>>1];j=(j-1)>>1;}
he[j]=x;
cnt++;
}
public void Pop(){
cnt--;
T r=he[cnt];
int j=0;
while(true){
if(j*2+10){j=j*2+1;}
else{j=j*2+2;}
}
else if(j*2>1;break;}
he[(j-1)>>1]=he[j];
}
he[j]=r;
}
private int Ao(T x,T y){return y.CompareTo(x);}
private int Do(T x,T y){return x.CompareTo(y);}
public T Top{get{return he[0];}}
private void Extend(){
T[] nhe=new T[max<<1];
Array.Copy(he,nhe,max);
he=nhe;
max<<=1;
}
}
public class Sc{
public int I{get{return int.Parse(Console.ReadLine());}}
public long L{get{return long.Parse(Console.ReadLine());}}
public double D{get{return double.Parse(Console.ReadLine());}}
public string S{get{return Console.ReadLine();}}
public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
public string[] Sa{get{return Console.ReadLine().Split();}}
public object[] Oa{get{return Console.ReadLine().Split();}}
public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
public int[] Ia3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),int.Parse);}
public int[] Ia3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),int.Parse);}
public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
public long[] La3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),long.Parse);}
public long[] La3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),long.Parse);}
public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
public double[] Da3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),double.Parse);}
public T[] Arr(int n,Func f){var a=new T[n];for(int i=0;i(int n,Func f){var a=new T[n];for(int i=0;i(int n,Func f){var a=new T[n];for(int i=0;i(int n,Func f){var a=new T[n];for(int i=0;i