Lou Smith's Form 1040, U.S. Individual Income Tax Return, for the 2016 year was due on April 15, 2017. On April 10, 2017, Lou Smith filed a valid extension that permitted him to file his 2016 Form 1040 on or before October 15, 2017. On July 15, 2017, Lou Smith mailed his 2016 Form 1040. On his 2016 Form, Lou Smith reported a tax liability of $60,000 and withholding credits of $50,000. Thus, Lou Smith owed $10,000. On July 20, 2017, the IRS received Lou Smith's 2016 Form 1040 along with the enclosed $10,000 check. Lou Smith paid no interest on the $10,000.In a notice and demand dated August 3, 2017, the IRS demanded that Lou Smith interest on the $10,000. On August 20, 2017, Lou paid the entire amount set forth in the notice and demand,

Question

 how many days of interest, if any, did Lou Smith pay on August 20, 2017?