1 struct Point{
 2     double x,y;
 3 };
 4 struct Line{
 5     Point p1,p2;
 6 };
 7 double Max(double a,double b)
 8 {
 9     return a>b?a:b;
10 }
11 double Min(double a,double b)
12 {
13     return a<b?a:b;
14 }
15 double xmulti(Point p1,Point p2,Point p0)
16 {
17     return (p1.x-p0.x)*(p2.y-p0.y)-(p1.y-p0.y)*(p2.x-p0.x);
18 }
19 bool inter(Line l1,Line l2)
20 {
21     if( Min(l2.p1.x,l2.p2.x)<=Max(l1.p1.x,l1.p2.x) &&
22         Min(l2.p1.y,l2.p2.y)<=Max(l1.p1.y,l1.p2.y) &&
23         Min(l1.p1.x,l1.p2.x)<=Max(l2.p1.x,l2.p2.x) &&
24         Min(l1.p1.y,l1.p2.y)<=Max(l2.p1.y,l2.p2.y) &&
25         xmulti(l1.p1,l2.p2,l2.p1)*xmulti(l1.p2,l2.p2,l2.p1)<=0 && 
26         xmulti(l2.p1,l1.p2,l1.p1)*xmulti(l2.p2,l1.p2,l1.p1)<=0 )
27         return true;
28     else 
29         return false;
30 }

 1 #include <iostream>
 2 using namespace std;
 3 struct Point{
 4     double x,y;
 5 };
 6 struct Line{
 7     Point p1,p2;
 8 };
 9 double Max(double a,double b)
10 {
11     return a>b?a:b;
12 }
13 double Min(double a,double b)
14 {
15     return a<b?a:b;
16 }
17 double xmulti(Point p1,Point p2,Point p0)
18 {
19     return (p1.x-p0.x)*(p2.y-p0.y)-(p1.y-p0.y)*(p2.x-p0.x);
20 }
21 bool inter(Line l1,Line l2)
22 {
23     if( Min(l2.p1.x,l2.p2.x)<=Max(l1.p1.x,l1.p2.x) &&
24         Min(l2.p1.y,l2.p2.y)<=Max(l1.p1.y,l1.p2.y) &&
25         Min(l1.p1.x,l1.p2.x)<=Max(l2.p1.x,l2.p2.x) &&
26         Min(l1.p1.y,l1.p2.y)<=Max(l2.p1.y,l2.p2.y) &&
27         xmulti(l1.p1,l2.p2,l2.p1)*xmulti(l1.p2,l2.p2,l2.p1)<=0 && 
28         xmulti(l2.p1,l1.p2,l1.p1)*xmulti(l2.p2,l1.p2,l1.p1)<=0 )
29         return true;
30     else 
31         return false;
32 }
33 int main()
34 {
35     int N;
36     Line l[105];
37     while(cin>>N){
38         if(N==0) break;
39         for(int i=1;i<=N;i++)
40             cin>>l[i].p1.x>>l[i].p1.y>>l[i].p2.x>>l[i].p2.y;
41         int c = 0;
42         for(int i=1;i<=N-1;i++)
43             for(int j=i+1;j<=N;j++)
44                 if(inter(l[i],l[j]))
45                     c++;
46         cout<<c<<endl;
47     }
48     return 0;
49 }