void main()
{
	double S(double ,double ,double ,double ,double );
	double a,b,c,d,sq,angle;
	scanf("%lf%lf%lf%lf%lf",&a,&b,&c,&d,&angle);
	sq=S(a,b,c,d,angle);
	if(sq==0) printf("Invalid input");
	else
	printf("%.4f",sq);
}
double S(double a,double b,double c,double d,double angle)
{
	double s,S,x,y;
	s=(a+b+c+d)/2;
	x=cos(angle/360*3.1415926);
	y=x*x;
	if(((s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*y)<0) return(0);
	else
	{
	S=sqrt((s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*y);
	return(S);
	}
}