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:
| Pos | Driver | Entrant | Constructor | Time/Retired | Grid |
| --- | --- | --- | --- | --- | --- |
| 1 | Jim Clark | Team Lotus | Lotus-Climax | 2.02:58.6 | 1 |
| 2 | Richie Ginther | Owen Racing Organisation | BRM | + 22.6 s | 3 |
| 3 | Graham Hill | Owen Racing Organisation | BRM | + 28.2 s | 2 |
| 4 | Jack Brabham | Brabham Racing Organisation | Brabham-Climax | + 52.0 s | 11 |
| 5 | Tony Maggs | Cooper Car Company | Cooper-Climax | 72 laps | 6 |
| 6 | Bruce McLaren | Cooper | Cooper-Climax | 72 laps | 7 |
| 7 | Mike Hailwood | Reg Parnell (Racing) | Lola-Climax | 70 laps | 9 |
| 8 | Ian Burgess | Scirocco-Powell (Racing Cars) | Scirocco-BRM | 69 laps | 18 |
| 9 | Peter Revson | Reg Parnell (Racing) | Lotus-BRM | 69 laps | 15 |
| 10 | Carel Godin de Beaufort | Ecurie Maarsbergen | Porsche | 67 laps | 20 |
| 11 | Jo Siffert | Siffert Racing Team | Lotus-BRM | Engine (66 laps) | 12 |
| 12 | André Pilette | André Pilette | Lotus-Climax | 63 laps | 21 |
| 13 | Innes Ireland | British Racing Partnership | Lotus-BRM | Oil pressure (56 laps) | 5 |
| 14 | Bernard Collomb | Bernard Collomb | Lotus-Climax | Oil pressure (46 laps) | 19 |
| Ret | Ian Raby | Ian Raby (Racing) | Gilby-BRM | Ignition | 13 |
| Ret | Dan Gurney | Brabham Racing Organisation | Brabham-Climax | Oil leak | 16 |
| Ret | Mike Beckwith | British Racing Partnership | Lotus-BRM | Accident | 17 |
| Ret | Masten Gregory | Tim Parnell | Lotus-BRM | Cam follower | 14 |
| Ret | Trevor Taylor | Team Lotus | Lotus-Climax | Crownwheel & pinion | 4 |
| Ret | Jo Bonnier | Rob Walker Racing Team | Cooper-Climax | Oil pressure | 8 |
| Ret | Tony Settember | Scirocco-Powell (Racing Cars) | Scirocco-BRM | Valve gear | 22 |
| Ret | Bob Anderson | DW Racing Enterprises | Lola-Climax | Gearbox | 10 |
| WD | Peter Arundell | Team Lotus | Lotus-Climax | Car not ready | - |
Question:
how many different drivers are listed?
Answer:
23