1 #include 
      
        2 #include 
       
         3  4 using namespace std; 5  6 struct line 7 { 8     double x1; 9     double y1;10     double x2;11     double y2;12 }l[110];13 14 bool test(int i,int j)15 {16     int s=0;17     double acd = (l[j].x1-l[i].x1)*(l[j].y1-l[j].y2) - (l[j].x1-l[j].x2)*(l[j].y1-l[i].y1);18     double bcd = (l[j].x1-l[i].x2)*(l[j].y1-l[j].y2) - (l[j].x1-l[j].x2)*(l[j].y1-l[i].y2);19     if(acd*bcd<=0)20         s++;21     double abd = (l[i].x1-l[j].x1)*(l[i].y1-l[i].y2) - (l[i].x1-l[i].x2)*(l[i].y1-l[j].y1);22     double abc = (l[i].x1-l[j].x2)*(l[i].y1-l[i].y2) - (l[i].x1-l[i].x2)*(l[i].y1-l[j].y2);23     if(abd*abc<=0)24         s++;25     if(s==2)26         return true;27     return false;28 }29 30 int main()31 {32     int n;33     while(scanf("%d",&n)!=EOF)34     {35         if(n==0)36             break;37         for(int i=0;i