using System;

namespace march24
{	
	public class UserAccount
	{
		/*
		 * A valid user name starts with a uppercase or lower case letter, 
		 * and contains no spaces.		
		*/
		public static bool IsValidName(string s)
		{
			if(( (s[0]>='a' && s[0]<='z')||(s[0]>='A' && s[0]<='Z'))
				&& (s.IndexOf(' ')==-1))
			{
				return true;
			}
			else
			{
				return false;
			}
			
		}

		public static void Main()
		{
			bool succ;
			do
			{
				Console.WriteLine("Create a user name");
				string s = Console.ReadLine();
				succ = IsValidName(s);
				if(succ)
					Console.WriteLine("okay");
				else
					Console.WriteLine("Invalid");
			}while(succ == false);
		}
	}
}