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 <vector>
#include <complex>
using namespace std;
typedef complex<double> P;
static const double EPS = 1e-8;

double dot(const P& p, const P& q)
{
  return p.real()*q.real() + p.imag()*q.imag();
}

double norm2(const P& p)
{
  return dot(p, p);
}

P perpendicular_foot(const P& p, const P line[2])
{
  const double t = dot(p - line[0], line[0] - line[1]) / norm2(line[0] - line[1]);
  return line[0] + t*(line[0]-line[1]);
}

bool intersect_point_segment(const P& p, const P seg[2])
{
  return abs(seg[0]-p) + abs(seg[1]-p) - abs(seg[1]-seg[0]) < EPS;
}

int main()
{
  int n;
  cin >> n;
  vector<pair<P,double> > walls(n);
  for (int i = 0; i < n; i++) {
    cin >> walls[i].first.real() >> walls[i].first.imag() >> walls[i].second;
  }
  int m;
  cin >> m;
  for (int i = 0; i < m; i++) {
    P taro, oni;
    cin >> taro.real() >> taro.imag() >> oni.real() >> oni.imag();
    const P line[] = {taro, oni};
    vector<pair<P,double> >::const_iterator it(walls.begin());
    for (; it != walls.end(); ++it) {
      const double d1 = abs(taro - it->first);
      const double d2 = abs(oni - it->first);
      if (d1 < it->second && d2 < it->second) {
      } else if (d1 > it->second && d2 > it->second) {
        const P h = perpendicular_foot(it->first, line);
        if (intersect_point_segment(h, line) && abs(h - it->first) - it->second < EPS) {
          cout << "Safe" << endl;
          goto NEXT;
        }
      } else {
        cout << "Safe" << endl;
        goto NEXT;
      }
    }
    cout << "Danger" << endl;
NEXT:
    ;
  }
  return 0;
}

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;
    }
    assert(0 <= u/c.r && u/c.r <= 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);

			bool f = true;
			for (int j = 0; j < n; j++) {
				L l;
				int cp = crossP(ci[j], L(t, s), l);
				if (!cp) continue;
				if (!ccw(t, s, l.x) || !ccw(t, s, l.y)) {
					f = false;
					break;
				}
			}
			if (f) {
				cout << "Danger" << endl;
			} else {
				cout << "Safe" << endl;
			}
		}
	}
	return 0;
}