using System;

​

public class Program

{

    static bool isValid(string s)

    {

        char c = s[0]; //prvi char

        if (!Char.IsUpper(c))  return false;

        if (Char.IsDigit(c))

        {

            return false;

        }

        return true;

    }

​

    static bool isAllLetters(string s)

    {

        if (s.Length == 0)

        {

            return false; //true

        }

​

        for (int i = 0; i < s.Length; i++)

        {

            char c = s[i]; //trenutni karakter

            if (Char.IsLetter(c)) //dali je c slovo

            {

            //do nothing

            }

            else

            {

                return false;

            }

        }

​

        return true;

    }

​

    public static void Main()

    {

        bool res = isAllLetters("Ana");

        Console.WriteLine("Hello World " + res);

        res = isAllLetters("1Ana");

        Console.WriteLine("Hello World " + res);

        res = isAllLetters("");

        Console.WriteLine("Hello World " + res);

        return;

    }

}