const double PI=3.1415926;
int main()
{
	int i;
	double a[6];
	for(i=0;i<5;i++)
	{
		scanf("%lf",&a[i]);
	}
	double area;
	double s;
	double temp;
	double angle=a[4]/180*PI;
	s=(a[0]+a[1]+a[2]+a[3])/2;
	temp=(s-a[0])*(s-a[1])*(s-a[2])*(s-a[3])-a[0]*a[1]*a[2]*a[3]*cos(angle/2)*cos(angle/2);
	if(temp<0)printf("Invalid input");
	else printf("%.4f",sqrt(temp));






	return 0;
}


		
		