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:
| No. in\nSeries | No. in\nSeason | Performer | Appearance | Air Date |
| --- | --- | --- | --- | --- |
| 268 | 1 | Tom Segura | only | 21 January 2011 |
| 269 | 2 | Michael Kosta | only | 21 January 2011 |
| 270 | 3 | Sheng Wang | only | 28 January 2011 |
| 271 | 4 | Chelsea Peretti | only | 28 January 2011 |
| 272 | 5 | Chris D'Elia | only | 4 February 2011 |
| 273 | 6 | Nate Bargatze | only | 4 February 2011 |
| 274 | 7 | Hari Kondabolu | only | 11 February 2011 |
| 275 | 8 | Jack Whitehall | only | 11 February 2011 |
| 276 | 9 | Al Jackson | only | 18 February 2011 |
| 277 | 10 | Kyle Kinane | only | 25 February 2011 |
| 278 | 11 | Matt Fulchiron | only | 25 February 2011 |
| 279 | 12 | Mike Vecchione | only | 4 March 2011 |
| 280 | 13 | Jessi Klein | only | 4 March 2011 |
| 281 | 14 | Louis Katz | only | 11 March 2011 |
| 282 | 15 | Jay Larson | only | 11 March 2011 |
| 283 | 16 | Natasha Leggero | only | 25 March 2011 |
Question:
how many performers appeared on the air date 21 january 2011?
Answer:
2