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

int n; 

struct hotel{
    
     
	
	int d;
	int c;
}a[10005];
int ans;


bool cmp  (hotel a,hotel b)
{
    
    
	
	if(a.d==b.d)
	{
    
    
		return a.c<b.c;
	}
	return a.d<b.d;
	
}

int main()
{
    
    
	while(scanf("%d",&n)==1 && n)
	{
    
    
		ans=0;
		
		for(int i=0;i<n;i++)
		{
    
    
			scanf("%d%d",&a[i].d,&a[i].c);
		}
		sort(a,a+n,cmp);
		
		for(int i=0;i<n;i++)
		{
    
    
			int ok=1;
			for(int j=0;j<i;j++)
			{
    
    
				if( (a[j].c<=a[i].c && a[j].d!=a[i].d)||(a[j].d==a[i].d && a[j].c<a[i].c))  
				{
    
    
					ok=0;
					break;
				}
				
			}
			if(ok)
				ans++; 			
		}		
		printf("%d\n",ans);
	}
	
	return 0;
}