JugarBoliche,
You are correct. Report them as either short term or long term capital gains with a cost of $0. IRS publication 550 ( https://www.irs.gov/pub/irs-pdf/p550.pdf ) page 23 states:
Nondividend distributions. Report nondividend distributions (box 3 of Form 1099-DIV) only after your basis in the stock has been reduced to zero. After the basis of your stock has been reduced to zero, you must show this excess amount on Form 8949, Part I, if you held the stock 1 year or less. Show it on Form 8949,
Part II, if you held the stock for more than 1 year. Enter the name of the company in column (a) of Form 8949. Report the amount of the excess distribution in column (d) and your zero basis in column (e) of Form 8949.
