void main()
{
	double a,b,c,d,t,z;
	double area(double a,double b,double c,double d,double t);
	scanf("%lf",&a);
	scanf("%lf",&b);
	scanf("%lf",&c);
	scanf("%lf",&d);
	scanf("%lf",&t);
	z=area(a,b,c,d,t);
	if(z<0)
		printf("Invalid input");
	else printf("%.4lf",sqrt(z));
}

double area(double a,double b,double c,double d,double t)
{     double y,s,PI = 3.1415926;
      s=(a+b+c+d)/2;
     y=(s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*cos(t/360*PI)*cos(t/360*PI);
	 return(y);
}