Since you inherited the stock in 2003 and assuming the Estate Adminstrator elected to use the valuation date that calculated the basis of your stock at $15,000, this effectively becomes your basis for tax purposes.
IRS has special rules for assigning valuation for inherited property. In fact, for you despite your basis is $0 dollars, you get a stepped up basis, to $15,000 and save paying taxes on $15,000 of capital gain.
Amir, you are one of the lucky taxpayers that the IRS has given a tax break for your situation. Your reportable gain is therefore $17,000 of long term gains!!