using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Ask("What is your name?");

    }

    public static string Ask(string question)

    {

        string input;

        do

        {

            Console.Write(question);

            input = Console.ReadLine();

​

        } while (input.Any(x => !char.IsLetter(x)));

        return input;

    }

}