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<cmath>
using namespace std;

class UFO{
public:
    int x0,y0,r,v;
    int IsDestroyed;
    UFO(){
        x0=0;
        y0=0;
        r=0;
        v=0;
        IsDestroyed = 0;
    }
    double get_distance(int t){
        return sqrt(1.0*x0*x0+1.0*y0*y0)-1.0*v*t;//???????????§????????¢
    }
};

int main(){
    int Radius,NumUFO;
    while(cin >> Radius >> NumUFO && (Radius|NumUFO)){
        int invasion=0;
        int i;
        UFO *u;
        u = new UFO[NumUFO];
        for(i=0;i<NumUFO;i++){
            cin >> u[i].x0 >> u[i].y0 >> u[i].r >> u[i].v;
        }
        int alive = NumUFO;
        int t=0;//??????
        for(i=0;i<NumUFO;i++){
            if(1.0*Radius > u[i].get_distance(t)){
                u[i].IsDestroyed = 1;
                alive--;
                invasion++;
            }
        }
        while(alive){//???????????£?????????UFO?????°???0??????????????§
            //?????????????\´???????????????
            int nearest;
            double vnearest = 100000.0;
            for(i=0;i<NumUFO;i++){
                if(u[i].IsDestroyed==0){
                    if(vnearest > u[i].get_distance(t)){
                        nearest = i;
                        vnearest = u[i].get_distance(t);
                    }
                }
            }
            //?????????????\´???????????£?????¬?????¶??????????°?
            //?????¨??´???????????¢?????¬?????¨??????
            int a = u[nearest].x0;
            int b = u[nearest].y0;
            for(i=0;i<NumUFO;i++){
                if(u[i].IsDestroyed==0){
                    //??????t????????????UFO???????????´????????????
                    double x,y;
                    x = 1.0*u[i].x0 - 1.0*u[i].x0*u[i].v*t/(sqrt(1.0*u[i].x0*u[i].x0+1.0*u[i].y0*u[i].y0));
                    y = 1.0*u[i].y0 - 1.0*u[i].y0*u[i].v*t/(sqrt(1.0*u[i].x0*u[i].x0+1.0*u[i].y0*u[i].y0));
                    if( (b*x-a*y)*(b*x-a*y) < 1.0*u[i].r*u[i].r*(a*a+b*b) && a*x + b*y > 0){
                        u[i].IsDestroyed = 1;
                        alive--;
                    }
                }
            }
            t++;//?¬?????????????
            for(i=0;i<NumUFO;i++){
                if(u[i].IsDestroyed==0){
                    if(1.0*Radius > u[i].get_distance(t)){
                        u[i].IsDestroyed = 1;
                        alive--;
                        invasion++;
                    }
                }
            }
        }
        cout << invasion << endl;
    }
    
    return 0;
}