/*
TASK: man
LANG: C++
*/
//Rumen Hristov Hristov

#include <stdio.h>
#include <algorithm>
#include <set>
using namespace std;

#define MAX 16384

int m;
set<int> a[ MAX ];

void solve()
{
    int i,j;
    int x,y;
    int ans;
    int n;
    
    ans = 0;
    n = 0;
    
    scanf ("%d",&m);
    
    for (i=1;i<=m;i++)
    {
        scanf ("%d%d",&x,&y);
        
        if ( x > n ) n = x;
        if ( y > n ) n = y;

        for (j=0;j<=n;j++)
        {
            if ( a[j].count(x) && a[j].count(y) )
            {
                break;
            }
        }
        
        if ( j == n+1 )
        {
            a[x].insert(y);
            a[y].insert(x);
            ans++;
        }
    }
    
    printf ("%d\n",ans);
}

int main()
{
    solve();
    
    return 0;
}
