1 bool quick_judge(point a,point b,point c,point d)
2 {
3     if(a.y>c.y||b.y<d.y||a.x>d.x||b.x<c.x)
4         return false;
5     else return true;
6 }

 1 bool cross_judge(point a,point b,point c,point d)
 2 {
 3     const double eps=1e-9;
 4     double ac,ad,cb,ca;
 5     ac=(c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);
 6     ad=(d.x-a.x)*(b.y-a.y)-(d.y-a.y)*(b.x-a.x);
 7     ca=(a.x-c.x)*(d.y-c.y)-(a.y-c.y)*(d.x-c.x);    //保险起见，把另一条边也判断一下
 8     cb=(b.x-c.x)*(d.y-c.y)-(b.y-c.y)*(d.x-c.x);
 9     if(ac*ad<eps&&ca*cb<eps) return true;
10     else return false;
11 }

 1 #include <bits/stdc++.h>
 2
 3 using namespace std;
 4
 5 const double eps=1e-9;
 6
 7 struct segment
 8 {
 9     double x1,x2,y1,y2;
10 }seg[2005];
11
12 bool judge(segment a,segment b)
13 {
14     if(min(a.x1,a.x2)<max(b.x1,b.x2)&&max(a.x1,a.x2)>min(b.x1,b.x2)&&min(a.y1,a.y2)<max(b.y1,b.y2)&&max(a.y1,a.y2)>min(b.y1,b.y2))
15     {
16         double v1,v2,v3,v4;
17         v1=(b.x1-a.x1)*(a.y2-a.y1)-(b.y1-a.y1)*(a.x2-a.x1);
18         v2=(b.x2-a.x1)*(a.y2-a.y1)-(b.y2-a.y1)*(a.x2-a.x1);
19         v3=(a.x1-b.x1)*(b.y2-b.y1)-(a.y1-b.y1)*(b.x2-b.x1);
20         v4=(a.x2-b.x1)*(b.y2-b.y1)-(a.y2-b.y1)*(b.x2-b.x1);
21         if(v1*v2<eps&&v3*v4<eps) return true;
22         else return false;
23     }
24     else return false;
25 }
26
27 int main()
28 {
29     int i,j,n,flag=0;
30     while(~scanf("%d",&n))
31     {
32         flag=0;
33         for(i=0;i<n;i++) scanf("%lf%lf%lf%lf",&seg[i].x1,&seg[i].y1,&seg[i].x2,&seg[i].y2);
34         for(i=0;i<n;i++)
35             for(j=i+1;j<n;j++)
36             {
37                 if(judge(seg[i],seg[j]))
38                 {
39                     flag=1;
40                     break;
41                 }
42             }
43         if(flag) printf("burned!\n");
44         else printf("ok!\n");
45     }
46     return 0;
47 }