hdu1785 You Are All Excellent

#include <stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
using namespace std;
#define PI 3.1415926535
struct point
{
	double x,y,s;
}m[101];

bool cmp(point a,point b){return a.s<b.s;}
int main(){
	int n,i;
	while(scanf("%d",&n) && n>=0){
		for(i=1;i<=n;i++){
			scanf("%lf%lf",&m[i].x,&m[i].y);
			if(m[i].x==0)
				m[i].s=PI/2;
			else if(m[i].x<0)
				m[i].s=atan(m[i].y/m[i].x)+PI;
			else
				m[i].s=atan(m[i].y/m[i].x);
		}

		sort(m+1,m+n+1,cmp);

		for(i=1;i<n;i++)
			printf("%.1lf %.1lf ",m[i].x,m[i].y);
		if(n!=0)
			printf("%.1lf %.1lf\n",m[i].x,m[i].y);
	}
    return 0;
}