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

class Program
{
    public void Solve()
    {
        int N = int.Parse(Console.ReadLine());
        Console.WriteLine(N % 2 == 0 ? N : N - 1);
    }

    static void Main()
    {
        var solver = new Program();
        solver.Solve();
    }
}