附上AC的code
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <cstring>
using namespace std;
struct position{
	float  x,y;
}arr[1010];
struct rangeofx{
	float left,right;
}range[1010];
bool cmpx(position a, position b){
return a.x<b.x;
}
bool cmpy(position a, position b){
return a.y>b.y;
}
float RD(float  c,float   b){
	return sqrt(c*c-b*b);
}
int main(){
	freopen("test.cpp","r",stdin);
	int  n,times=1;
	float d;
	while(~scanf("%d %f",&n,&d)){
		memset(arr,0,sizeof(arr));
		memset(range,0,sizeof(range));
		int flag=0;
		
		if(n==0&&d==0){
			break;
		}
		for(int i=0;i<n;i++){
			scanf("%f %f",&arr[i].x,&arr[i].y);
			if(arr[i].y>d)
				flag=1;

		}
		if(flag==1){
			printf("Case %d: -1\n",times);times++;
			continue;
		}
		sort(arr,arr+n,cmpy);
		sort(arr,arr+n,cmpx);
		for(int i=0;i<n;i++){
			range[i].left=arr[i].x-RD(d,arr[i].y);
			range[i].right=arr[i].x+RD(d,arr[i].y);
		}
		int  ans = 1;  
    	float  tmp = range[0].right;
            for(int i = 1;i < n;i ++)
            {
                if(tmp < range[i].left)
                {
                   ans ++;
                   tmp = range[i].right;
                }
                if(tmp > range[i].right)
           		     tmp = range[i].right;
            }
		printf("Case %d: %d\n",times,ans);
		times++;
	}
	return 0;
}