double solve()
{
u.read();v.read();
int k1,k2;
k1=mid((u-v).angle());
k2=mid((v-u).angle());
double t1=(u-v)*(p[k1]-v);
double t2=(u-v)*(p[k2]-v);
if(t1*t2>-eps)return 0.0;
double s1,s2;
P a,b;
s1=s2=0.0;
a=calc(k1,k2,s1,s2);
b=calc(k2,k1,s2,s1);
s1+=a*b;
s2+=b*a;
return min(s1,s2)/2.0;
}
