using static System.Console;

using static System.Math;

using System.Globalization;

​

namespace Uri_CSharp {

    public class URI {

        public static void Main(string[] args) {

            if (double.TryParse(ReadLine(), out var raio)) {

                double area = Pow(raio, 2) * 3.14159;

                WriteLine(area.ToString("F4", new CultureInfo("pt-BR")));

            }

        }

    }

}