int main()
{
	double s,a,b,c,d,o,S;
	scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
	scanf("%lf",&o);
	s=1.0/2.0*(a+b+c+d);
	if (((s-a)*(s-b)*(s-c)*(s-d) - a*b*c*d*cos(o*3.1415926/180/2)*cos(o*3.1415926/180/2))<0)
	{printf("Invalid input");
	return 0;}
	S=sqrt((s-a)*(s-b)*(s-c)*(s-d) - a*b*c*d*cos(o*3.1415926/180/2)*cos(o*3.1415926/180/2));
	printf("%.4lf\n",S);
	return 0;
}

	

