int main()
{
	double PI,a,b,c,d,s,S,p,o;
	PI=3.1415926;

scanf("%lf %lf %lf %lf %lf",&a,&b,&c,&d,&p);
s=(a+b+c+d)/2;
o=p/360*2*PI/2;
double x=(s-a)*(s-b)*(s-c)*(s-d);
	S=sqrt((s-a)*(s-b)*(s-c)*(s-d)-a*b*c*d*cos(o)*cos(o));
	if(x<0)
	{printf("Invalid input");
	}
else
{printf("%.4lf",S);}
return 0;
}