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++: #include<iostream>
#include<algorithm>
#include<vector>
#include<utility>
#include<cmath>
using namespace std;
#define X first
#define Y second

typedef long double ld;
typedef long long ll;
typedef ld P_type;
//typedef pair<P_type,P_type> P;
typedef pair<int,int> P;
const ld INF = 1e39;
const ld EPS = 1e-8;
const ld  PI = acos(-1);

P operator-(P a,P b) {
  return P(a.X - b.X, a.Y - b.Y);
}

P_type out_pro(P a,P b) {
  return (a.X * b.Y - b.X * a.Y);
}

P_type in_pro(P a,P b){
  return (a.X * b.X + a.Y *b.Y);
}

P_type pow_len(P a) {
  return a.X * a.X + a.Y * a.Y;
}

ld len(P a){
  return sqrt(ld(pow_len(a)));
}

struct UFO{
  UFO(){};
  UFO(ld xx,ld yy,int rr,int vv){
    pos.X=xx;
    pos.Y=yy;
    r=rr;
    v=vv;
  }
  P pos;
  int r,v;
};
ld distance(UFO a,int time){
  return len(a.pos)-double(time*a.v);
}
int t;//now time
bool operator<(UFO a,UFO b){
  return distance(a,t)<distance(b,t);
}


int R;
vector<UFO> ufos;
void init(){
  t=1;
  R=0;
  ufos.clear();
}

bool input(){
  int n;
  cin>>R>>n;
  if(R==0&&n==0)return false;
  for(int i=0;i<n;i++){
    ld x,y;
    int r,v;
    cin>>x>>y>>r>>v;
    ufos.push_back(UFO(x,y,r,v));
  }
  return true;
}

bool shot(UFO target,UFO aa,int time){
  P tar = target.pos;
  P a = aa.pos;
  P tmp = a;
  ld nlen=(len(tmp)-(aa.v*time));
  a.X = tmp.X*nlen/len(tmp);
  a.Y = tmp.Y*nlen/len(tmp);
  ld dist = abs(out_pro(tar,a));
  return (aa.r+EPS >= dist/len(tar))&&(in_pro(tar,a)>=0)&&(distance(aa,t)>R-EPS);
}


int solve(){
  int res=0;
  while(ufos.size()!=0){
    vector<UFO> tmp;
    sort(ufos.begin(),ufos.end());
    UFO target;
    bool j=false;
    for(int i=0;i<ufos.size();i++){
      if(distance(ufos[i],t)<=R+EPS){
        res++;
      }else{
        if(j){
          if(!shot(target,ufos[i],t)){
            tmp.push_back(ufos[i]);
          }
        }else{
          target=ufos[i];
          j=true;
        }
      }
    }
    ufos=tmp;t++;
  }
  return res;
}

int main(){
  while(init(),input()){
    cout<<solve()<<endl;
  }
}

C++: #include <bits/stdc++.h>
using namespace std;

#define EPS (1e-9)
#define EQUALS(a, b) (fabs((a) - (b)) < EPS)
#define SQR(n) ((n) * (n))
#define DIST(ax, bx, ay, by) (sqrt(SQR((ax) - (bx)) + SQR((ay) - (by))))

struct UFO
{
    double x, y, r, v;

    UFO () {}
    UFO (double x, double y, double r, double v) : x(x), y(y), r(r), v(v) {}

    void move()
    {
        double dx, dy;
        double rr = dist();

        dx = v * (x / rr), dy = v * (y / rr);
        if ( !EQUALS(x, 0.0) || !EQUALS(y, 0.0) ) {
            if ( fabs(x) < fabs(dx) - EPS ) {
                x = EPS, y = EPS;
            } else {
                x -= dx, y -= dy;
            }
        }
    }

    double dist()
    {
        return ( sqrt(SQR(x) + SQR(y)) );
    }

    bool laser(double bx, double by, double R)
    {
        double dot   = (x - R * bx) * bx + (y - R * by) * by;
        double cross = (x - R * bx) * by - (y - R * by) * bx;
        if ( dot < -EPS ) {
            return (DIST(x, R * bx, y, R * by) < r - EPS);
        } else {
            return ( cross < r - EPS);
        }
    }
};


int main()
{
    int R, N;

    UFO ufo[105];

    while ( cin >> R >> N, R || N ) {

        for ( int i = 0; i < N; i++ ) {
            double x, y, r, v;
            cin >> x >> y >> r >> v;
            ufo[i] = UFO(x, y, r, v);
        }

        int cnt = 0;
        bool isfinished[105] = {};
        while ( true ) {
            int minp = -1;
            double minv;

            for ( int i = 0; i < N; i++ ) {
                ufo[i].move();
                //cout << ufo[i].x << " " << ufo[i].y << endl;
                double d = ufo[i].dist();
                if ( !isfinished[i] && d > (double)R + EPS && (minp == -1 || minv > d + EPS) ) {
                    minv = d, minp = i;
                }
            }
            //cout << minp << endl;
            if ( minp == -1 ) {
                break;
            } else {
                double x = ufo[minp].x / ufo[minp].dist(), y = ufo[minp].y / ufo[minp].dist();

                isfinished[minp] = true;
                for ( int i = 0; i < N; i++ ) {
                    if ( !isfinished[i] && ufo[i].laser(x, y, (double)R) ) {
                        isfinished[i] = true;
                    }
                }
            }
        }
        for ( int i = 0; i < N; i++ ) {
            if ( !isfinished[i] ) {
                cnt++;
            }
        }
        cout << cnt << endl;
    }

    return ( 0 );
}