static void Main(string[] args)
{
Console.WriteLine("Herfi daxil edin.");
byte[] characters = Encoding.ASCII.GetBytes(Console.ReadLine());
Console.WriteLine();
byte[] previous = { Convert.ToByte(characters[0] - 1) };
char[] previousCharacter = Encoding.ASCII.GetChars(previous);
Console.WriteLine($"Evvelki simvol: {previousCharacter[0]}");
byte[] next = { Convert.ToByte(characters[0] + 1) };
char[] nextCharacter = Encoding.ASCII.GetChars(next);
Console.WriteLine($"Sonrakı simvol: {nextCharacter[0]}");
Console.ReadLine();
}