Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	x := make([]int, 100)
	y := make([]int, 100)
	r := make([]int, 100)
	for scanner.Scan() {
		a, _ := strconv.Atoi(scanner.Text())
		if a == 0 {
			break
		}
		for i := 0; i < a; i++ {
			scanner.Scan()
			input := strings.Split(scanner.Text(), " ")
			tmpx, _ := strconv.Atoi(input[0])
			tmpy, _ := strconv.Atoi(input[1])
			tmpr, _ := strconv.Atoi(input[2])
			x[i], y[i], r[i] = tmpx, tmpy, tmpr
		}
		scanner.Scan()
		b, _ := strconv.Atoi(scanner.Text())
		for i := 0; i < b; i++ {
			scanner.Scan()
			input := strings.Split(scanner.Text(), " ")
			c, _ := strconv.Atoi(input[0])
			d, _ := strconv.Atoi(input[1])
			e, _ := strconv.Atoi(input[2])
			f, _ := strconv.Atoi(input[3])
			ok := false
			for j := 0; j < a; j++ {
				if (c-x[j])*(c-x[j])+(d-y[j])*(d-y[j]) >= r[j]*r[j] || (e-x[j])*(e-x[j])+(f-y[j])*(f-y[j]) >= r[j]*r[j] {
					if (e-c)*(x[j]-c)+(f-d)*(y[j]-d) < 0 {
						if (x[j]-c)*(x[j]-c)+(y[j]-d)*(y[j]-d) <= r[j]*r[j] {
							ok = true
						}
					} else {
						if (e-c)*(x[j]-c)+(f-d)*(y[j]-d)>(e-c)*(e-c)+(f-d)*(f-d) {
							if (x[j]-e)*(x[j]-e)+(y[j]-f)*(y[j]-f)<=r[j]*r[j] {
								ok = true
							}
						} else {
							if (x[j]-c)*(x[j]-c)+(y[j]-d)*(y[j]-d)-((e-c)*(x[j]-c)+(f-d)*(y[j]-d))*((e-c)*(x[j]-c)+(f-d)*(y[j]-d))/((e-c)*(e-c)+(f-d)*(f-d))<=r[j]*r[j] {
								ok = true
							}
						}
					}

				}
			}
			if ok {
				fmt.Println("Safe")
			} else {
				fmt.Println("Danger")
			}
		}
	}
}

C++: #include <iostream>
#include <complex>
#include <cmath>
using namespace std;

int main()
{
	int n, m;
	complex<double> w[100];
	int r[100];

	cin >> n;

	while (n > 0) {
		for (int i = 0; i < n; i++) {
			double x, y;

			cin >> x >> y >> r[i];
			w[i] = complex<double> (x, y);
		}

		cin >> m;

		for (int j = 0; j < m; j++) {
			double tx, ty, sx, sy;
			complex<double> t, s;
			bool f = 1;

			cin >> tx >> ty >> sx >> sy;
			t = complex<double>(tx, ty);
			s = complex<double>(sx, sy);

			for (int i = 0; i < n; i++) {
				if ((abs(t - w[i]) - r[i]) * (abs(s - w[i]) - r[i]) <= 0)
					f = 0;
				else if(abs(t - w[i]) > r[i] && abs(s - w[i]) > r[i]){

					if (abs(arg((t - s) / (w[i] - s))) <= asin(r[i] / abs(w[i] - s))
						&& abs(t - s) * abs(t - s) >= abs(w[i] - s) * abs(w[i] - s) - r[i] * r[i])
						f = 0;
				}
			}

			if (f)
				cout << "Danger" << endl;
			else
				cout << "Safe" << endl;
		}

		cin >> n;
	}

	return 0;
}

C++: #include <iostream>
#include <cmath>

using namespace std;

#define NMAX 100

struct S1{
	int wx, wy, r;
};

/*点と円 true->点は円の内部*/
bool po_cr(int cx, int cy, int cr, int px, int py){
	return pow((cx - px), 2.0) + pow((cy - py), 2.0) <= pow(cr, 2.0);
}

/*円と線 true->接している*/
bool li_cr(int cx, int cy, int cr,int lx1, int ly1, int lx2, int ly2){

	double A, B, C, CA, AS, BS;
	double d;

	A = sqrt(pow(cx - lx1, 2.0) + pow(cy - ly1, 2.0));
	B = sqrt(pow(cx - lx2, 2.0) + pow(cy - ly2, 2.0));
	C = sqrt(pow(lx1 - lx2, 2.0) + pow(ly1 - ly2, 2.0));
	CA = (lx2 - lx1) * (cy - ly1) - (cx - lx1) * (ly2 - ly1);
	AS = (cx - lx1) * (lx2 - lx1) + (cy - ly1) * (ly2 - ly1);
	BS = (cx - lx2) * (lx2 - lx1) + (cy - ly2) * (ly2 - ly1);

	if(C != 0) d = CA / C;
	else d = 0;

	if(d <= cr){
		if(AS * BS <= 0){
			return 1;
		}
		else if(cr > A || cr > B){
			return 1;
		}
	}
	return 0;
}

int main(){

	int n, m;
	S1 wall[NMAX];
	int tx, ty, sx, sy;
	bool f1, f2;

	while(1){

		cin >> n;
		if(n == 0) break;

		for(int i = 0; i < n; i++){
			cin >> wall[i].wx >> wall[i].wy >> wall[i].r;
		}

		cin >> m;

		for(int i = 0; i < m; i++){

			cin >> tx >> ty >> sx >> sy;

			f1 = true;
			for(int j = 0; j < n; j++){
				if(po_cr(wall[j].wx, wall[j].wy, wall[j].r, tx, ty)!=po_cr(wall[j].wx, wall[j].wy, wall[j].r, sx, sy)){
					f1 = false;
				}
			}
			
			f2 = true;
			for(int j = 0; j < n; j++){
				if(!po_cr(wall[j].wx, wall[j].wy, wall[j].r, sx, sy)){
					if(li_cr(wall[j].wx, wall[j].wy, wall[j].r, tx, ty, sx, sy)){
						f2 =  false;
					}
				}
			}

			if(f1 && f2 ) cout << "Danger" << endl;
			else cout << "Safe" << endl;
		}
	}

}

C++: #include <iostream>
#include <map>
#include <queue>
#include <algorithm>
#include <complex>
#include <cassert>

using namespace std;
typedef long long ll;

typedef long double R;
typedef complex<R> P;


namespace std {
    bool operator < (P a, P b) {
        return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
    }
    bool operator > (P a, P b) {
        return (b < a);
    }
}

const R EPS = 1e-7;
const R PI = acos(-1);

int sgn(R a) {
    if (a < -EPS) return -1;
    if (a > EPS) return 1;
    return 0;
}


bool near(P a, P b) {
    return !sgn(abs(a-b));
}

R cross(P a, P b) { return imag(conj(a)*b); }
R dot(P a, P b) { return real(conj(a)*b); }

/* 1->cclock
  -1->clock
   0->on
   2->back
  -2->front
  */
int ccw(P a, P b, P c) {
    assert(!near(a, b));
    if (near(a, c) || near(b, c)) return 0;
    int s = sgn(cross(b-a, c-a));
    if (s) return s;
    if (a > b) swap(a, b);
    if (c < a) return 2;
    if (b < c) return -2;
    return 0;
}

struct L {
    P x, y;
    L() {};
    L(P x, P y) :x(x), y(y) {};
};

R abs(const L &l) {
    return abs(l.y - l.x);
}

struct C {
    P p;
    R r;
    C () {};
    C (P p, R r) : p(p), r(r) {};
};

R distLP(const L &l, const P &p) {
	assert(!near(l.x, l.y));
    return abs(cross(l.y-l.x, p-l.x)/abs(l));
}

//need Intersect/distLP
int crossP(const C &c, const L &l, L &r) {
    R u = distLP(l, c.p);
    int si = sgn(u - c.r);
    if (si == 1) return 0;
    P v = (l.y-l.x) / abs(l) * P(0, -1); //l?????´???????????????????????????
    v *= c.r;
    if (ccw(l.x, l.y, c.p) < 0) v *= -1;
    //v?????????????????????l?????¨??????????????????????????????
    if (si == 0) {
    	r.x = r.y = c.p + v;
    	return 1;
    }

    R th = acos(u/c.r);
    r.x = c.p+v*polar<R>(1.0,-th);
    r.y = c.p+v*polar<R>(1.0,th);
    return 2;
}

C ci[110];
int main() {
	while (true) {
		int n;
		cin >> n;
		if (!n) break;
		for (int i = 0; i < n; i++) {
			R x, y, r;
			cin >> x >> y >> r;
			ci[i] = C(P(x, y), r);
			assert(r);
		}
		int m;
		cin >> m;
		for (int i = 0; i < m; i++) {
			R tx, ty, sx, sy;
			cin >> tx >> ty >> sx >> sy;
			P t = P(tx, ty), s = P(sx, sy);
			L l;
			bool f = true;
			for (int j = 0; j < n; j++) {
				L l;
				int cp = crossP(ci[j], L(t, s), l);
//				printf("%d %d %d %Lf\n", i, j, cp, distLP(L(t, s), ci[j].p) );
				if (!cp) continue;
//				cout << l.x << " " << l.y << endl;
//				cout << abs(l.x - ci[j].p) << " " << abs(l.y - ci[j].p) << endl;
				if (!ccw(t, s, l.x) || !ccw(t, s, l.y)) {
					//printf("%d %d\n", i, j);
					f = false;
					//break;
				}
			}
			if (f) {
				cout << "Danger" << endl;
			} else {
				cout << "Safe" << endl;
			}
		}
	}
	return 0;
}