6.2

#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
struct edge
{
double l,r;
};
edge e[1010];
int n,d;
bool cmp(edge a,edge b)
{
if(a.r!=b.r)
return a.r<b.r;
return a.l>b.l;
}
int main()
{
scanf("%d%d",&n,&d);
for(int i=1;i<=n;i++)
{
int x,y;
scanf("%d%d",&x,&y);
e[i].l=(x-sqrt(double(d*d-y*y)));
e[i].r=(x+sqrt(double(d*d-y*y)));
}
sort(e+1,e+1+n,cmp);
double now=e[1].r;
int ans=1;
for(int i=2;i<=n;i++)//选择原理：紫书P233区间选点问题，核心是贪心。
{
if(now<=e[i].r&&now>=e[i].l)
continue;
else
ans++,now=e[i].r;
}
printf("%d\n",ans);
return 0;
}