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

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            int ch;
            var l = 0;
            string s = Console.ReadLine();
            string[] w = s.Split(' ');
            try
            {
                foreach (var el in w)
                {
                    ch = int.Parse(el);
                    if (ch > 20 && ch < 40)
                    {
                        l = ch;
                        Console.WriteLine(l);
                    }
                }
            }
            catch (System.FormatException e)
            {
                Console.WriteLine(e.Message);
            }
        }
    }
}