double m(double a,double b,double c,double d,double e)
{
	double pi,s,sq;
	s=(a+b+c+d)/2;
	pi=3.1415926;
	sq=sqrt((s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*cos(pi*e/360)*cos(pi*e/360));
	return(sq);
}

void main()
{
	double m(double a,double b,double c,double d,double e);
	double a,b,c,d,e,p,s;
	scanf("%lf%lf%lf%lf%lf",&a,&b,&c,&d,&e);
	s=(a+b+c+d)/2;
	if((s-a)*(s-b)*(s-c)*(s-d)<0)
		printf("Invalid input");
	else
	{p=m(a,b,c,d,e);
	printf("%.4lf\n",p);}
}
