using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var c = double.Parse(Console.ReadLine());
            var rr = Console.ReadLine().Split(' ').Select(x => double.Parse(x)).ToArray();
            var r = (rr[1] - rr[0]) / 2;
            var R = rr[0] + r;
            var pi = 3.14159265358979323846264338327950288;
            Console.WriteLine(2 * pi * pi * r * r * R * c);
        }
    }
}