using System;

namespace krtuch
{
    class Program
    {
        const double F1 = -490.0, F2 = 740;
        const double r1 = 0.02, r2 = 0.035;
        const double d = 0.36;

        static void Main(string[] args)
        {
            double r = Math.Cbrt(r1*r1*r1 + r2*r2*r2);
            double Q = 0;
            for (int i = 0; i < 100; ++i) {
                Q += q(i) + _q(i);
            }
            Console.WriteLine(Q / r);
        }

        static double q(int i) {
            if (i == 0) {
                return F1 * r1;
            }

            return -r1 * _q(i - 1) / (d - _s(i-1));
        }

        static double _q(int i) {
            if (i == 0) {
                return F2 * r2;
            }

            return -r2 * q(i - 1) / (d - s(i-1));
        }


        static double s(int i) {
            if (i == 0) {
                return 0;
            }

            return r1 * r1 / (d - _s(i-1));
        }

        static double _s(int i) {
            if (i == 0) {
                return 0;
            }

            return r2 * r2 / (d - s(i-1));
        }
    }
}