static string[] post = new string[]{ "", "Thousand", "Million", "Billion", "Trillion", "Quadrillion", "Quintillion" }; public static void Main()
Console.Write("Enter a whole number: "); string input = Console.ReadLine();
if(!int.TryParse(input, out vl))
Console.WriteLine("Invalid input."); int amountOfDigits = input.ToString().Length;
while(index < input.Length)
if((amountOfDigits - index - 1) % 3 == 0)
output += " " + post[(amountOfDigits - index - 1) / 3] + " ";
Console.WriteLine(output);
