using System;

public class Program

{

    public static void Main()

    {

        ReadInteger();

    }

    public static void ReadInteger()

    {

        string text;

        do

        {

            text = Console.ReadLine();

        }

        while(!IsNum(text));

        int num = Convert.ToInt32(text);

        Console.WriteLine(num);

    }

    public static bool IsNum(string text)

    {

        try

        {

            Convert.ToInt32(text);

            return true;

        }

        catch

        {

            Console.WriteLine("Not a number");

            return false;

        }

    }

}