using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("1234567 = " + formatSku("123"));     // normal sku

        Console.WriteLine("1234567A = " + formatSku("123A"));   // subsku

        Console.WriteLine("12Z3A = " + formatSku("12Z3A"));   // invalid sku

    }

    public static string formatSku(string sku) {

        string formattedSku = "";

        int numericSku = 0;

        if(Int32.TryParse(sku, out numericSku)) {

            // normal sku, format it to 8 digits with leading zeros

            formattedSku = numericSku.ToString("00000000");

        } else {

            // non numeric sku, determine if it is subsku

            // removing last character should make it numeric

            string mainSku = sku.Substring(0, sku.Length - 1);

            if(Int32.TryParse(mainSku, out numericSku)) {

                // sub sku, format it to 8 digits with leading zeros followed by the subsku character

                formattedSku = numericSku.ToString("00000000") + sku.Substring(sku.Length - 1, 1);

            } else {

                // not a valid sku

                formattedSku = sku;

            }

        }

        return formattedSku;

    }

}