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

#define N_MAX 100

class Point {
public:
  double x, y;
  Point(double x=0, double y=0) : x(x), y(y) {}
  Point operator + (Point p) { return Point(x + p.x, y + p.y); }
  Point operator - (Point p) { return Point(x - p.x, y - p.y); }
};
typedef Point Vector;

class Segment {
public:
  Point p1, p2;
  Segment(Point p1, Point p2) {
    this->p1 = p1;
    this->p2 = p2;
  }
};

typedef Segment Line;

class Circle {
public:
  Point o;
  double r;
};


double norm(Vector a) { return a.x*a.x + a.y*a.y; }
double abs(Vector a) { return sqrt(norm(a)); }
double dot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }
double cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }

double getDistanceSP(Segment s, Point p) {
  if(dot(s.p2 - s.p1, p - s.p1) < 0) return abs(p - s.p1);
  if(dot(s.p1 - s.p2, p - s.p2) < 0) return abs(p - s.p2);
  return fabs(cross(s.p2 - s.p1, p - s.p1)) / abs(s.p2 - s.p1);
}

bool isInCircle(Circle c, Point p) {
  return c.r - abs(c.o - p) >= 0;
}

int n;
vector<Circle> w(N_MAX);
Point t, s;


void solve() {
  {
    vector<Circle>::iterator it = w.begin();
    while(it != w.end()) {
      bool tic, sic;
      tic = isInCircle(*it, t);
      sic = isInCircle(*it, s);
      if(tic && sic) {
	it = w.erase(it);
      } else if(tic || sic) {
	cout << "Safe" << endl;
	return;
      } else {
	it++;
      }
    }
  }

  Segment u(t, s);
  for(int i = 0; i < w.size(); ++i) {
    if(w[i].r - getDistanceSP(u, w[i].o) >= 0) {
      cout << "Safe" << endl;
      return;
    }
  }
  cout << "Danger" << endl;
}

main() {
  while((cin >> n) && n) {
    w.clear();
    for(int i = 0; i < n; ++i) {
      Circle c;
      cin >> c.o.x >> c.o.y >> c.r;
      w.push_back(c);
    }
    int m;
    cin >> m;
    for(int i = 0; i < m; ++i) {
      cin >> t.x >> t.y >> s.x >> s.y;
      solve();
    }
  }
}

C++: #include <iostream>
#include <vector>
#include <map>
#include <stack>
#include <list>
#include <queue>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <math.h>

#define DEBUG 0
#define NITENKAN(a, b) sqrt(((a.first - b.first) * (a.first - b.first)) + ((a.second - b.second) * (a.second - b.second)))

using namespace std;

bool checkFound(pair<double, double> taro, pair<double, double> oni, pair<pair<double, double>, double> syougai){
	double ac = NITENKAN(syougai.first, oni);
	double ab = NITENKAN(taro, oni);
	double bc = NITENKAN(syougai.first, taro);

	double SOnaiseki =  (taro.first - oni.first) * (syougai.first.first - oni.first) + (taro.second - oni.second) * (syougai.first.second - oni.second);
	double TOnaiseki =  (oni.first - taro.first) * (syougai.first.first - taro.first) + (oni.second - taro.second) * (syougai.first.second - taro.second);
	double SOcosSita = SOnaiseki / (ab * ac);
	double TOcosSita = TOnaiseki / (ab * bc);
	
	if(SOcosSita < 0 || TOcosSita < 0){
		return true;
	}
	//垂線部分の高さ成分
	double SOt = SOnaiseki / (ab * ab);//ac * (1 - cosSita);//(sita * 3.14 / 180.0));
	double TOt = TOnaiseki / (ab * ab);//ac * (1 - cosSita);//(sita * 3.14 / 180.0));
	double SOhc = ac - (SOt * ab);
	double TOhc = bc - (TOt * ab);
	double gaiseki = (syougai.first.first - oni.first) * (taro.second - oni.second) - (taro.first - oni.first) * (syougai.first.second - oni.second);
	double hc = gaiseki / ab;

#if DEBUG
	cout << "SOcosSita1 : " << SOcosSita << endl;
	cout << "TOcosSita2 : " << TOcosSita << endl;
	cout << "SOt : " << SOt << endl;
	cout << "TOt : " << TOt << endl;
	cout << "syougai.second : " << syougai.second << endl;
	cout << "SOhc : " << SOhc << endl;
	cout << "TOhc : " << TOhc << endl;
#endif

	if(hc >= syougai.second){
		return true;
	}
	else{
		return false;
	}
}

int main(){
	int n = 0;

	while(cin >> n && n != 0){
		int m = 0;
		bool danger = false;
		vector<pair<pair<double, double>, double> > syougai(n);

		for(int i = 0; i < n; i++){
			cin >> syougai[i].first.first >> syougai[i].first.second >> syougai[i].second;
		}
		
		cin >> m;
		vector<pair<double, double> > taro(m);
		vector<pair<double, double> > oni(m);
		for(int j = 0; j < m; j++){
			//cinと比較、結果出力を書く
			cin >> taro[j].first >> taro[j].second >> oni[j].first >> oni[j].second;

			//太郎と鬼の現在位置における各障害物の影響を見る
			for(int l = 0; l < n; l++){
				//二人共円内
				if((NITENKAN(taro[j], syougai[l].first) < syougai[l].second) && (NITENKAN(oni[j], syougai[l].first) < syougai[l].second)){
					/*//円内に円がある可能性があるので他の障害物の影響を見る
					for(int a = l + 1; a < n; a++){
						danger = checkFound(taro[j], oni[j], syougai[a]);
						//障害物により安全とわかった段階で抜ける
						if(!danger){
							break;
						}
					}
					*/
					danger = true;
				}
				//二人共円外
				else if((NITENKAN(taro[j], syougai[l].first) > syougai[l].second) &&  (NITENKAN(oni[j], syougai[l].first) > syougai[l].second)){
					danger = checkFound(taro[j], oni[j], syougai[l]);
				}
				else{
					danger = false;
				}
				if(!danger){
					break;		
				}
			}

			if(!danger){
				cout << "Safe" << endl;
			}
			else{
				cout << "Danger" << endl;
			}

		}
	}
}