using System;

public class Program

{

    public static void Main()

    {

        int n = int.Parse(Console.ReadLine());

        int max = 0

        while(n > 0)

       {

          if(max < n && n % 2 == 1)

          {

             max = n

          }

        }

          }

            if(max m 0)

          {

            Console.WriteLine(max);

          }

            else

          {

}