#include <iostream>

#include <algorithm>

#include <cstdio>

#include <cmath>

using namespace std;

const int MAXN=10100;

struct Village{

	double l,r;

};

Village p[MAXN];

bool cmp(Village A, Village B){

	if(A.l<B.l)return true;

	else if(A.l==B.l){

		if(A.r<B.r)return true;

	}

	return false;

}

int main(){

	int n,L,D; double x,y;

	while(scanf("%d%d%d",&L,&D,&n)!=EOF){

		for(int i=0;i<n;i++){

			scanf("%lf%lf",&x,&y);

			double d=sqrt(D*D-y*y);

			p[i].l=x-d; p[i].r=x+d;

		}

		int counted=1;

		sort(p,p+n,cmp);

		double s=p[0].r;

		for(int i=1;i<n;i++){

			if(p[i].l<=s)

			continue;

			else{

				s=p[i].r;

				counted++;

			}

		}

		printf("%d\n",counted);

	}

	return 0;

}