#include <stdio.h>
# define dim 50001


long n, x[dim], y[dim], i, j, k;

int main()
{
	freopen("pachete.in","r",stdin);
	freopen("pachete.out","w",stdout);

	scanf("%ld",&n);
	for(i=0; i<=n; i++)
		scanf("%ld %ld",&x[i],&y[i]);
	for(i=1; i<=n; i++)
	{
		if(x[i]>=0)
		for(j=i+1; j<=n; j++)
		{
			if(y[i]<=y[0])
			{
				if((y[i]+x[i]==y[j]+x[j] || y[i]+x[i]==y[j]+x[j]+1 )&& y[j]<=y[0])
				{
					x[j]=-1;
					k++;
				}
			}
			else
			{
				if(y[i]-x[i]==y[j]-x[j] || y[i]-x[i]==y[j]-x[j]-1 && y[j]>y[0])
				{
					x[j]=-1;
					k++;
				}
			}
		}
	}
       printf("%ld",n-k);
	return 0;
}