int main()
{
	double a,b,c,d,e,s,S,f,D;

	scanf("%lf%lf%lf%lf%lf",&a,&b,&c,&d,&e);
	s=(a+b+c+d)/2; 
	f=e*3.1415926/(2*180);
    D=(s-a)*(s-b)*(s-c)*(s-d) - a*b*c*d*cos(f)*cos(f);
    if(D>=0)
	{
	    S = sqrt((s-a)*(s-b)*(s-c)*(s-d) - a*b*c*d*cos(f)*cos(f));	
		printf("%.4lf",S);
	}
	if(D<0)
	{
		printf("Invalid input");
	}
return 0;
}
