HDU1086

#include    
#include    
  
#define eps 1e-8   
#define zero(x) (((x)>0 (x):-(x))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)





>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;  
    }  
}