/*
TASK:man
LANG:C++
*/
#include <iostream>
using namespace std;
char a[5685][5685]={{0},{0}};
int N=0,M;
int check(int wh,int tar)
{
 int i,p;
 for(i=0;i<N;i++)
   if(a[wh][i]==1 && a[i][tar]==1)return 0;
 a[wh][tar]=1;
 a[tar][wh]=1;
 return 1;
}

int main()
{
 int i,a,b,how=0;
 cin>>M;
 for(i=0;i<M;i++)
  {
   cin>>a>>b;
   if(b>N)N=b;
   if(a>N)N=a;
   how+=check(a,b);
  }
 cout<<how<<endl;
 return 0;
}
