double mj(float a,float b,float c,float d,float e)
{
    
	double t,s,k;
    k=(double)3.1415926*e/360;
	s=(a+b+c+d)/2;
	if(((s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*cos(k)*cos(k))<0)
	{
		t=-1;
	}
	else
    {
	t=sqrt((s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*cos(k)*cos(k));
	}
	return(t);
}
void main()
{

	double f;
    float a,b,c,d,e;
	scanf("%f%f%f%f%f",&a,&b,&c,&d,&e);
	f=mj(a,b,c,d,e);
	if(f<0)
	{printf("Invalid input");}
	else
	{printf("%.4f",f);}
}
