C# program for converting a number into words (spell)

using System;
//wirtten by Suneel Gudipati
namespace NumberToWords
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] units = new string[] { "ONE ", "TWO ", "THREE ", "FOUR ", "FIVE ", "SIX ", "SEVEN ", "EIGHT ", "NINE ", "TEN ", "ELEVEN ", "TWELEVE ", "THIRTEEN ", "FOURTEEN ", "FIFTEEN ", "SIXTEEN ", "SEVENTEEN ", "EIGHTEEN ", "NINTEEN " };
            string[] tens=new string[]{"TEN ","TWENTY ","THIRTY ","FOURTY ","FIFTY ","SIXTY ","SEVENTY ","EIGHTY ","NINTY "};
            int i,num;
            string result="";
            Console.Write("Enter number here in range 1-999 : ");
            num = int.Parse(Console.ReadLine());
            if (num >99&&num<1000)
            {
                i=num/100;
                result=units[i-1]+"HUNDRED ";
                num =num%100;
            }//if
            if (num>19&&num<100)
            {
                i=num/10;
                result =result+tens[i-1];
                num=num%10;
            }//if
            if (num<20&&num>0)
                result+=units[num-1];
            Console.WriteLine("The number you entered: "+result);
            Console.ReadLine();
        }
    }
}