using System;

class Program

    {

        static int charToInt(char letter)

        {

            int numericalChar = (letter - '0');

            return numericalChar;

        }

        static char GetCapitalChar()

        {

            char Letter = 'a';

            while (Letter < 'A' || Letter > 'Z')

            {

                Console.WriteLine("please insert a CAPITAL letter");

                Letter = char.Parse(Console.ReadLine());

            }

            return Letter;

        }

        static char GetChar(char A, char B)

        {

            char Letter = '0';

            if (A<B)

            {

                while (Letter > A && Letter < B)

                {

                    Console.WriteLine("not good char, insert new char.");

                    Letter = char.Parse(Console.ReadLine());

                }

            }

        }

        static void Main(string[] args)

        {

            char capitalletter=GetCapitalChar();

            Console.WriteLine(capitalletter);

        }

    }

​