Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Series # | Title | Directed by | Written by | Original air date | Production code | U.S. viewers (million) |
| --- | --- | --- | --- | --- | --- | --- |
| 1.0 | " Pilot " | Anthony Russo & Joe Russo | Dan Harmon | September17,2009 | 100.0 | 7.89 |
| 2.0 | " Spanish 101 " | Joe Russo | Dan Harmon | September24,2009 | 101.0 | 5.39 |
| 3.0 | " Introduction to Film " | Anthony Russo | Tim Hobert & Jon Pollack | October1,2009 | 102.0 | 5.86 |
| 4.0 | " Social Psychology " | Anthony Russo | Liz Cackowski | October8,2009 | 104.0 | 4.87 |
| 5.0 | " Advanced Criminal Law " | Joe Russo | Andrew Guest | October15,2009 | 105.0 | 5.01 |
| 6.0 | " Football, Feminism and You " | Joe Russo | Hilary Winston | October22,2009 | 103.0 | 5.18 |
| 7.0 | " Introduction to Statistics " | Justin Lin | Tim Hobert & Jon Pollack | October29,2009 | 106.0 | 5.32 |
| 8.0 | " Home Economics " | Anthony Russo | Lauren Pomerantz | November5,2009 | 107.0 | 5.45 |
| 9.0 | " Debate 109 " | Joe Russo | Tim Hobert | November12,2009 | 109.0 | 5.09 |
| 10.0 | " Environmental Science " | Seth Gordon | Zach Paez | November19,2009 | 108.0 | 4.86 |
| 11.0 | " The Politics of Human Sexuality " | Anthony Russo | Hilary Winston | December3,2009 | 110.0 | 5.42 |
| 12.0 | " Comparative Religion " | Adam Davidson | Liz Cackowski | December10,2009 | 111.0 | 5.51 |
| 13.0 | " Investigative Journalism " | Joe Russo | Jon Pollack & Tim Hobert | January14,2010 | 113.0 | 5.42 |
| 14.0 | " Interpretive Dance " | Justin Lin | Lauren Pomerantz | January21,2010 | 112.0 | 4.73 |
| 15.0 | " Romantic Expressionism " | Joe Russo | Andrew Guest | February4,2010 | 115.0 | 5.23 |
| 16.0 | " Communication Studies " | Adam Davidson | Chris McKenna | February11,2010 | 116.0 | 5.15 |
| 17.0 | " Physical Education " | Anthony Russo | Jessie Miller | March4,2010 | 118.0 | 5.06 |
| 18.0 | " Basic Genealogy " | Ken Whittingham | Karey Dornetto | March11,2010 | 117.0 | 4.70 |
| 19.0 | " Beginner Pottery " | Anthony Russo | Hilary Winston | March18,2010 | 114.0 | 5.21 |
| 20.0 | " The Science of Illusion " | Adam Davidson | Zach Paez | March25,2010 | 122.0 | 5.07 |
| 21.0 | " Contemporary American Poultry " | Tristram Shapeero | Emily Cutler & Karey Dornetto | April22,2010 | 123.0 | 3.67 |
| 22.0 | " The Art of Discourse " | Adam Davidson | Chris McKenna | April29,2010 | 124.0 | 4.36 |
| 23.0 | " Modern Warfare " | Justin Lin | Emily Cutler | May6,2010 | 119.0 | 4.35 |
| 24.0 | " English as a Second Language " | Gail Mancuso | Tim Hobert | May13,2010 | 120.0 | 4.49 |
Question:
What is the highest series # directed by ken whittingham?
Answer:
18.0