

double s(double a,double b,double c,double d)

{

        double s;

        s=(a+b+c+d)/2;

        return (s);

}

double cos2(double r)

{

        double k,i;

        k=cos(r/2*3.1415926/180);

        i=k*k;

        return (i);

}

void main()

{

        double S,temp;

        double a, b, c, d, r;

        scanf("%lf",&a);

        scanf("%lf",&b);

        scanf("%lf",&c);

        scanf("%lf",&d);

        scanf("%lf",&r);

        temp=(s(a,b,c,d)-a)*(s(a,b,c,d)-b)*(s(a,b,c,d)-c)*(s(a,b,c,d)-d) - a*b*c*d*cos2(r);

        if (temp<0)

               printf("Invalid input\n");

        else

        {

               S=sqrt(temp);

               printf("%.4lf",S);

        }

}

