public static void Main()
Console.WriteLine("Menu");
Console.WriteLine("Press 1 Input data[5]");
Console.WriteLine("Press 2 Display sum");
Console.WriteLine("Press 3 Display average");
Console.WriteLine("Press 4 Exit");
Console.Write("Please enter menu : ");
menu = Console.ReadLine();
Console.WriteLine("Your choose 1st menu");
Console.WriteLine("Your choose 2nd menu");
Console.WriteLine("Your choose 3rd menu");
Console.WriteLine("Your choose 4th menu");
Console.WriteLine("Please choose 1-4th menu only");