using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        string pattern=@"([a-zA-Z0-9]+)@([a-zA-Z0-9]+).com$";

        string pattern2=@"^([a-zA-Z0-9]+)@([a-zA-Z0-9]+).org$";

        string s=Console.ReadLine();

        Match m=Regex.Match(s,pattern);

        Match m1=Regex.Match(s,pattern2);

        if(m.Success || m1.Success)

        {

            Console.WriteLine("valid");

        }

        else

            Console.WriteLine("invalid");

    }

}