#include <iostream>#include <stdio.h>#include <cmath>#include <algorithm>#include <string.h>using namespace std;int L,d;struct I{ double l,r;}inter[10000];bool cmp(I a ,I b){ if(a.r<b.r) return true; else if(a.r==b.r) { if(a.l>b.l) return true; return false; } return false;}int main(){ double x,y; while(scanf("%d",&L)!=EOF) { scanf("%d",&d); int n; cin>>n; for(int i=1;i<=n;i++) { scanf("%lf%lf",&x,&y); inter[i].l=x-sqrt(d*d-y*y); inter[i].r=x+sqrt(d*d-y*y); } sort(inter+1,inter+1+n,cmp); int ans=1; double temp=inter[1].r; for(int i=2;i<=n;i++) { if(temp>L) temp=L; if(temp<inter[i].l) { ans++; temp=inter[i].r; } } cout<<ans<<endl; } return 0;}
