private static int getProduct(int[] arr)
    {
        int product = 1;
        foreach(int x in arr)
            product *= x;
        return product;
    }
    
    public static void printAnswer(string num, int n, int k)
    {
        int highestProduct = 0;
        int c = n-k+1; //max combinations
        for(int i = 0; i < c; i++)
        {
            string newStr = num.Substring(i,k);
            int [] arr = newStr.Select(x => x - '0').ToArray();
            int product = getProduct(arr);
            if(product > highestProduct)
            {
                highestProduct = product;
            }
        }
        Console.WriteLine(highestProduct);
    }