
/*
ID: C055
TASK: man
LANG: C++
*/

#include <iostream>
#include <set>
using namespace std;

void solve()
{
    set<int> diff;
    
    int N;
    scanf( "%d", &N );
    
    for( int i = 0, t; i < N*2; ++i )
    {
        scanf( "%d", &t );
        diff.insert( t );
    }
    
    printf( "%d\n", diff.size()-1 );
}

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