HDU1086

#include <iostream>   
#include <math.h>   
  
#define eps 1e-8   
#define zero(x) (((x)>0?(x):-(x))<eps)   
  
using namespace std;  
  
struct point  
{  
    double x,y;  
};  
  
struct line  
{  
    point a,b;  
};  
  
double xmult(point p1,point p2,point p0)  
{  
    return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);  
}  
  
bool dots_inline(point p1,point p2,point p3)  
{  
    return zero(xmult(p1,p2,p3));  
}  
  
bool same_side(point p1,point p2,line l)  
{  
    return xmult(l.a,p1,l.b)*xmult(l.a,p2,l.b)>eps;  
}  
  
bool dot_online_in(point p,line l)  
{  
    return zero(xmult(p,l.a,l.b))&&(l.a.x-p.x)*(l.b.x-p.x)<eps&&(l.a.y-p.y)*(l.b.y-p.y)<eps;  
}  
  
bool intersect_in(line u,line v)  
{  
    if (!dots_inline(u.a,u.b,v.a)||!dots_inline(u.a,u.b,v.b))  
        return !same_side(u.a,u.b,v)&&!same_side(v.a,v.b,u);  
    return dot_online_in(u.a,v)||dot_online_in(u.b,v)||dot_online_in(v.a,u)||dot_online_in(v.b,u);  
}  
  
int main()  
{  
    int n;  
    while(cin>>n && n)  
    {  
        line l[105];  
        for(int i = 1; i <= n; i++)  
        {  
            cin >> l[i].a.x >> l[i].a.y >> l[i].b.x >> l[i].b.y;  
        }  
        int cnt = 0;  
        for(int i = 1; i < n; i++)  
        {  
            for(int j = i + 1; j <= n; j++)  
            {  
                if(intersect_in(l[i], l[j]))  
                {  
                    cnt++;  
                }  
            }  
        }  
        cout << cnt << endl;  
    }  
}