You don't need a converter for a laptop PC/Mac. Their power adapters work with both standards. You will just need a plug adapter. You can get it in Ukraine for less than a buck.

If you plan to bring and use other appliances in Ukraine, you WILL NEED a power adapter. You can get it in RadioShack or Fri's Electronics (if you're in the South West) or just search it on ebay if you have time.