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<cmath>
#include<cstdlib>
using namespace std;
struct Point{
	Point():x(0),y(0){}
	Point(int x,int y):x(x),y(y){}
	int x,y;
};
struct Circle{
	Point p;
	int r;
};
/* _a,b©ç£ÌñæðÔ·Ö */
int DistanceSquared( Point a, Point b ){
	return ( a.x - b.x ) * ( a.x - b.x ) + ( a.y - b.y ) * ( a.y - b.y );
}
/* ¾YASA éÇÌîñ©çA»êçÌÊuÖWªSafe©Danger©²×éÖ */
bool IsSafePlace( Circle c, Point taro, Point dem ){
	double vx1, vy1, vx2, vy2, alpha1, alpha2;
	int seki = ( (taro.x - c.p.x) * ( dem.x - taro.x ) + (taro.y - c.p.y) * (dem.y - taro.y ) );
	int D = seki * seki - DistanceSquared(taro,dem) * ( DistanceSquared(c.p,taro) - c.r * c.r );

	if( D < 0 )
		return false;

	//cout << DistanceSquared(taro, dem) << endl;

	alpha1 = ( -seki - sqrt((double)D) ) / DistanceSquared(taro, dem);
	alpha2 = ( -seki + sqrt((double)D) ) / DistanceSquared(taro, dem);

	//cout << alpha1 << "," << alpha2 << endl;

	vx1 = (taro.x - c.p.x) + alpha1 * ( dem.x - taro.x );
	vy1 = (taro.y - c.p.y) + alpha1 * ( dem.y - taro.y );
	vx2 = (taro.x - c.p.x) + alpha2 * ( dem.x - taro.x );
	vy2 = (taro.y - c.p.y) + alpha2 * ( dem.y - taro.y );

	//cout << px + c.p.x << ' ' << py + c.p.y << endl;

	if( ( vx1 * (taro.y - c.p.y) - (taro.x - c.p.x) * vy1 ) *
		( vx1 * (dem.y  - c.p.y) - (dem.x  - c.p.x) * vy1 ) > 0 &&
		( vx2 * (taro.y - c.p.y) - (taro.x - c.p.x) * vy2 ) *
		( vx2 * (dem.y  - c.p.y) - (dem.x  - c.p.x) * vy2 ) > 0)
		return false;
	else
		return true;
}
int main(void){
	while(true){
		int n, m;
		vector<Circle> vWall;

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

		for(int i = 0; i < n; ++i){
			Circle tc;
			cin >> tc.p.x >> tc.p.y >> tc.r;
			vWall.push_back( tc );
		}

		cin >> m;

		for(int i = 0; i < m; ++i){
			bool safe = false;
			Point p_taro, p_daemon;
			cin >> p_taro.x >> p_taro.y >> p_daemon.x >> p_daemon.y;

			for( unsigned int j = 0; j < vWall.size(); ++j ){
				if( IsSafePlace( vWall[j], p_taro, p_daemon ) ){
					safe = true;
					cout << "Safe\n";
					break;
				}
			}
			if( !safe ){
				cout << "Danger\n";
			}
		}
	}
}

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;
	cout << "gaiseki : " << gaiseki << endl;
	cout << "hc : " << hc << endl;
#endif
	if(hc < 0) hc *= -1;
	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;
			}

		}
	}
}