static void Main(string[] args)
{
    double area, raio , pi;
    pi = 3.14159;
    raio = Convert.ToDouble(Console.ReadLine());
    area = pi * Math.Pow(raio,2);
    Console.WriteLine("A={0}n",area.ToString("N0"));
}

using static System.Console;
using static System.Math;

public class Program {
    public static void Main(string[] args) {
        if (double.TryParse(ReadLine(), out var raio)) WriteLine($"A = {PI * Pow(raio, 2):N4}");
    }
}