Go: package main

import (
	"bufio"
	"os"
	"math"
	"strings"
	"strconv"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

const (
	INF = 0x7FFFFFFF
	EPS = 1e-10
)

type Point struct {
	x, y float64
}
func (p *Point) plus(q *Point) *Point {
	return &Point{p.x + q.x, p.y + q.y}
}
func (p *Point) minus(q *Point) *Point {
	return &Point{p.x - q.x, p.y - q.y}
}
func (p *Point) multi(a float64) *Point {
	return &Point{p.x * a, p.y * a}
}
func (p *Point) div(a float64) *Point {
	return &Point{p.x / a, p.y / a}
}
func (p *Point) abs() float64 {
	return math.Sqrt(p.norm())
}
func (p *Point) norm() float64 {
	return p.x*p.x + p.y*p.y
}
func (p *Point) isLessThan(q *Point) bool {
	if p.x != q.x {
		return p.x < q.x && p.y < q.y
	}
	return true
}
func (p *Point) isEqual(q *Point) bool {
	return math.Abs(p.x - q.x) < EPS && math.Abs(p.y - q.y) < EPS
}

type Segment struct {
	p1, p2 *Point
}
func (s *Segment) norm() float64 {
	return (s.p2.x - s.p1.x)*(s.p2.x - s.p1.x) +
		(s.p2.y - s.p1.y)*(s.p2.y - s.p1.y)
}
func (s *Segment) abs() float64 {
	return math.Sqrt(s.norm())
}

func norm(a *Point) float64 {
	return a.x*a.x + a.y*a.y
}

func abs(a *Point) float64 {
	return math.Sqrt(norm(a))
}

func polar(a, r float64) *Point {
	return &Point{math.Cos(r)*a, math.Sin(r)*a}
}

func getDistance(a, b *Point) float64 {
	return abs(a.minus(b))
}

func dot(a, b *Point) float64 {
	return a.x*b.x + a.y*b.y
}

func cross(a, b *Point) float64 {
	return a.x*b.y - a.y*b.x
}

func getDistanceLP(s Segment, p *Point) float64 {
	return cross(s.p2.minus(s.p1), p.minus(s.p1))/ abs(s.p2.minus(s.p1))
}

func getDistanceSP(s Segment, p *Point) float64 {
	if dot(s.p2.minus(s.p1), p.minus(s.p1)) < 0 {
		return abs(p.minus(s.p1))
	}
	if dot(s.p1.minus(s.p2), p.minus(s.p2)) < 0 {
		return abs(p.minus(s.p2))
	}
	return getDistanceLP(s, p)
}

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		R, _ := strconv.Atoi(buf[0])
		N, _ := strconv.Atoi(buf[1])
		if R == 0 && N == 0 {
			break
		}
		p := make([]*Point, N)
		r := make([]float64, N)
		v := make([]float64, N)
		d := make([]float64, N)
		nd := make([]float64, N)
		die := make([]bool, N)
		for i := 0; i < N; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			_x, _ := strconv.ParseFloat(buf_[0], 64)
			_y, _ := strconv.ParseFloat(buf_[1], 64)
			_r, _ := strconv.ParseFloat(buf_[2], 64)
			_v, _ := strconv.ParseFloat(buf_[3], 64)
			tmp := &Point{_x, _y}
			p[i] = tmp
			r[i] = _r
			v[i] = _v
			nd[i] = getDistance(p[i], &Point{0, 0})
			d[i] = getDistance(p[i], &Point{0, 0})
			die[i] = false
		}
		for {
			for i := 0; i < N; i++ {
				nd[i] = math.Max(float64(R), nd[i]-v[i])
			}
			mini := float64(INF)
			id := -1
			for i := 0; i < N; i++ {
				if die[i] {
					continue
				}
				if nd[i] < EPS+float64(R) {
					continue
				}
				if nd[i] > mini {
					continue
				}
				mini = nd[i]
				id = i
			}
			if id == -1 {
				break
			}
			s := Segment{p[id], p[id]}
			s.p1 = s.p1.div(d[id])
			s.p1 = s.p1.multi(float64(R))
			s.p2 = s.p2.div(d[id])
			s.p2 = s.p2.multi(10000000.0)
			for i := 0; i < N; i++ {
				if nd[i] < EPS + float64(R) {
					continue
				}
				a := p[i]
				a = a.div(d[i])
				a = a.multi(nd[i])
				if getDistanceSP(s, a) < EPS + r[i] {
					die[i] = true
				}
			}
		}
		ans := 0
		for i := 0; i < N; i++ {
			if !die[i] {
				ans++
			}
		}
		fmt.Println(ans)
	}
}

C++: // 2012/08/08 Tazoe

#include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;

struct UFO{
	int x0;
	int y0;
	int r;
	int v;

	double d;
	double x;
	double y;
};

bool d_desc(const UFO& left, const UFO& right)
{
	return left.d > right.d;
}

int main()
{
	while(true){
		int R, N;
		cin >> R >> N;

		if(R==0&&N==0)
			break;

		struct UFO U[100];
		for(int i=0; i<N; i++){
			cin >> U[i].x0 >> U[i].y0 >> U[i].r >> U[i].v;
		}

		for(int i=0; i<N; i++){
			U[i].d = sqrt((double)(U[i].x0*U[i].x0+U[i].y0*U[i].y0));
			U[i].x = (double)U[i].x0;
			U[i].y = (double)U[i].y0;
		}

		int M = 0;

		while(N){
			sort(U, U+N, d_desc);
//			for(int i=0; i<N; i++){
//				cout << U[i].d << ' ' << U[i].x << ' ' << U[i].y << endl;
//			}

			for(int i=N-1; i>=0; i--){
				if(U[i].d<=(double)R){
					M++;
					N--;
				}
				else
					break;
			}

			double D = U[N-1].d;
			double X = U[N-1].x;
			double Y = U[N-1].y;

			N--;

			for(int i=N-1; i>=0; i--){
				double d = U[i].x*Y-U[i].y*X;
				if(d<0.0)
					d = -d;
				d /= D;
//				cout << d << ' ' << U[i].r << endl;

				if(d<=(double)U[i].r&&U[i].x*X>=0.0&&U[i].y*Y>=0.0){
					for(int j=i; j<N-1; j++){
						U[j] = U[j+1];
					}
					N--;
				}

			}

//			cout << M << ' ' << N << endl;

			for(int i=0; i<N; i++){
				double d_pre = U[i].d;
				U[i].d -= (double)U[i].v;
				if(U[i].d<0.0)
					U[i].d = 0.0;

				U[i].x = U[i].x*U[i].d/d_pre;
				U[i].y = U[i].y*U[i].d/d_pre;
			}
		}

		cout << M << endl;
	}

	return 0;
}

C++: #include<iostream>
#include<complex>
#include<vector>
#include<algorithm>
#include<cmath>

using namespace std;

template<class T> T sqr(T x){
  return x*x;
}

const double eps=1e-9;

int main(){
  for(int R,N;cin>>R>>N,R;){
    int x0[100],y0[100],r[100],v[100];
    vector<int> rem(N);
    for(int i=0;i<N;i++){
      cin>>x0[i]>>y0[i]>>r[i]>>v[i];
      rem[i]=i;
    }
    int ans=0;
    for(int i=1;;i++){
      auto d=[&](int x){
	return sqrt(sqr(x0[x])+sqr(y0[x]))-i*v[x];
      };
      auto it=remove_if(begin(rem),end(rem),[&](int x){
	  return d(x)<=R+eps;
	});
      ans+=end(rem)-it;
      rem.erase(it,end(rem));
      if(rem.empty())break;
      auto cl=min_element(begin(rem),end(rem),[&](int a,int b){
	  return d(a)<d(b);
	});
      rem.erase(remove_if(begin(rem),end(rem),[&](int x){
	    complex<double> rp=polar(d(x),atan2(y0[x],x0[x])-atan2(y0[*cl],x0[*cl]));
	    return rp.real()>0&&(rp.imag()+r[x])*(rp.imag()-r[x])<=eps;
	  }),end(rem));
    }
    cout<<ans<<endl;
  }
}