#include<iostream.h>
int main()
{
	long a[50000],b[50000],i,n,j,p,q;
	int c[50000]={0},t=0;
	while(1)
	{
		p=0,q=0;
		cin>>n;
		t++;
		if(n==0)
			break;
		for(i=0;i<n;i++)
			cin>>a[i]>>b[i];
		for(i=0;i<n;i++)
		if(c[i]!=t)
		{
			for(j=i+1;j<n;j++)
			{
				if((a[j]>=a[i])&&(b[j]>=b[i]))
				{
					c[i]=t;
					break;
				}
				if((a[j]<=a[i])&&(b[j]<=b[i]))
					c[j]=t;
			}	
			if(c[i]!=t)
				q++;
		}
		cout<<q<<endl;
	}
	return 0;
}