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 <cstdio>
#include <cmath>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <set>
#include <cassert>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,j) FOR(i,0,j)
#define mp std::make_pair

typedef long long ll;
typedef unsigned long long ull;

const int INF = 1001001001;

// S N E W(南北東西)
const int dx[8] = {0, 0, 1, -1, 1, 1, -1, -1}, dy[8] = {1, -1, 0, 0, 1, -1, 1, -1};

struct P{
    P(){}
    P(ll _r, ll _i):r(_r), i(_i){}
    void real(const ll& v){r = v;}
    void imag(const ll& v){i = v;}
    ll r, i;
};

ll real(const P& p){return p.r;}
ll imag(const P& p){return p.i;}
ll norm(const P& p){ll r = real(p), i = imag(p); return r * r + i * i;}

P operator+(const P& lhs, const P& rhs){
    return P(real(lhs)+real(rhs), imag(lhs)+imag(rhs));
}
P operator-(const P& lhs, const P& rhs){
    return P(real(lhs)-real(rhs), imag(lhs)-imag(rhs));
}
P operator-(const P& p){
    return P(-real(p), -imag(p));
}

ll cross(const P& lhs, const P& rhs){
    return real(lhs)*imag(rhs) - imag(lhs)*real(rhs);
}

ll dot(const P& lhs, const P& rhs){
    return real(lhs)*real(rhs) + imag(lhs)*imag(rhs);
}

ll distance(const P& a, const P& b, const P& p){
    ll c = cross(p-a, b-a);
    return c * c;
}

bool doesLineCrossCircle(const P& a, const P& b, const P& cc, const ll& radius){
    if(distance(a, b, cc) > radius * radius * norm(b-a)){return false;}
    if(norm(a-cc) > radius * radius && norm(b-cc) > radius * radius){
        return dot(cc-a, b-a) * dot(cc-b, b-a) <= 0;
    }
    return (norm(a-cc) < radius * radius) ^ (norm(b-cc) < radius * radius);
}

int N, M;
P wps[100100]; ll wrs[100100];

int main(){
    while(std::cin >> N, N){
        assert(N < 100100);
        REP(i, N){
            ll re, im;
            std::cin >> re >> im >> wrs[i];

            wps[i].real(re); wps[i].imag(im);
        }

        std::cin >> M;
    
        REP(i, M){
            P taro, oni;
            ll re, im;
            std::cin >> re >> im;
            taro.real(re); taro.imag(im);
            std::cin >> re >> im;
            oni.real(re); oni.imag(im);

            bool f = false;
            REP(j, N){
                assert(norm(taro-wps[j]) != wrs[j] * wrs[j] &&
                       norm(oni-wps[j]) != wrs[j] * wrs[j]);
                if(real(taro) == real(oni) &&
                   imag(taro) == imag(oni)){
                    continue;
                }
                if(doesLineCrossCircle(taro, oni, wps[j], wrs[j])){
                    f = true;
                }
            }

            if(f){
                puts("Safe");
            }else{
                puts("Danger");
            }
        }
    }
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <set>
#include <cassert>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,j) FOR(i,0,j)
#define mp std::make_pair

typedef long long ll;
typedef unsigned long long ull;

const int INF = 1001001001;

// S N E W(南北東西)
const int dx[8] = {0, 0, 1, -1, 1, 1, -1, -1}, dy[8] = {1, -1, 0, 0, 1, -1, 1, -1};

struct P{
    P(){}
    P(ll _r, ll _i):r(_r), i(_i){}
    void real(const ll& v){r = v;}
    void imag(const ll& v){i = v;}
    ll r, i;
};

ll real(const P& p){return p.r;}
ll imag(const P& p){return p.i;}
ll norm(const P& p){ll r = real(p), i = imag(p); return r * r + i * i;}

P operator+(const P& lhs, const P& rhs){
    return P(real(lhs)+real(rhs), imag(lhs)+imag(rhs));
}
P operator-(const P& lhs, const P& rhs){
    return P(real(lhs)-real(rhs), imag(lhs)-imag(rhs));
}
P operator-(const P& p){
    return P(-real(p), -imag(p));
}

ll cross(const P& lhs, const P& rhs){
    return real(lhs)*imag(rhs) - imag(lhs)*real(rhs);
}

ll dot(const P& lhs, const P& rhs){
    return real(lhs)*real(rhs) + imag(lhs)*imag(rhs);
}

ll distance(const P& a, const P& b, const P& p){
    ll c = cross(p-a, b-a);
    return c * c;
}

bool doesLineCrossCircle(const P& a, const P& b, const P& cc, const ll& radius){
    if(distance(a, b, cc) > radius * radius * norm(b-a)){return false;}
    if(norm(a-cc) > radius * radius && norm(b-cc) > radius * radius){
       return dot(cc-a, b-a) * dot(cc-b, b-a) <= 0;
    }
    return (norm(a-cc) < radius * radius) ^ (norm(b-cc) < radius * radius);
}

int N, M;
P wps[100100]; ll wrs[100100];

int main(){
    while(std::cin >> N, N){
        assert(N < 100100);
        REP(i, N){
            ll re, im;
            std::cin >> re >> im >> wrs[i];

            wps[i].real(re); wps[i].imag(im);
        }

        std::cin >> M;
    
        REP(i, M){
            P taro, oni;
            ll re, im;
            std::cin >> re >> im;
            taro.real(re); taro.imag(im);
            std::cin >> re >> im;
            oni.real(re); oni.imag(im);

            bool f = false;
            REP(j, N){
                // assert(norm(taro-wps[j]) != wrs[j] * wrs[j] &&
                //       norm(oni-wps[j]) != wrs[j] * wrs[j]);
                // if(real(taro) == real(oni) &&
                //    imag(taro) == imag(oni)){
                //     continue;
                // }
                if(doesLineCrossCircle(taro, oni, wps[j], wrs[j])){
                    f = true;
                }
            }

            if(f){
                puts("Safe");
            }else{
                puts("Danger");
            }
        }
    }
}