

int main()
{
	double a,b,c,d;
	double sum,hudu;
	double s;
	double pi=3.1415926;
	double m;    

	scanf("%lf%lf%lf%lf%lf",&a,&b,&c,&d,&sum);
	m=1.0/2*(a+b+c+d);
	hudu=sum*pi/180;

	if ((m-a)*(m-b)*(m-c)*(m-d) - a*b*c*d*cos(hudu/2)*cos(hudu/2)<0)
	{
		printf("Invalid input");
		return 0;	
	}
	else 
	{
		s = sqrt((m-a)*(m-b)*(m-c)*(m-d) - a*b*c*d*cos(hudu/2)*cos(hudu/2));
	}
	printf("%.4lf\n",s);
	return 0;
}