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

namespace yuki
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            if (N % 2 == 0) Console.WriteLine(N);
            else Console.WriteLine(N - 1);
        }
    }
}