using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder
{
    class Abc162F
    {
        public static void Main()
        {
            var n = int.Parse(Console.ReadLine());
            var ans = (22 / 7) * n * n;
            Console.Write(ans);
        }
    }
}
