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:
| Rd. | Grand Prix | Date | Location | Pole Position | Fastest Lap | Winning Driver | Constructor | Report |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | Brazilian Grand Prix | 26 March | Jacarepaguá | Ayrton Senna | Riccardo Patrese | Nigel Mansell | Ferrari | Report |
| 2 | San Marino Grand Prix | 23 April | Imola | Ayrton Senna | Alain Prost | Ayrton Senna | McLaren-Honda | Report |
| 3 | Monaco Grand Prix | 7 May | Monaco | Ayrton Senna | Alain Prost | Ayrton Senna | McLaren-Honda | Report |
| 4 | Mexican Grand Prix | 28 May | Hermanos Rodríguez | Ayrton Senna | Nigel Mansell | Ayrton Senna | McLaren-Honda | Report |
| 5 | United States Grand Prix | 4 June | Phoenix | Ayrton Senna | Ayrton Senna | Alain Prost | McLaren-Honda | Report |
| 6 | Canadian Grand Prix | 18 June | Circuit Gilles Villeneuve | Alain Prost | Jonathan Palmer | Thierry Boutsen | Williams-Renault | Report |
| 7 | French Grand Prix | 9 July | Paul Ricard | Alain Prost | Maurício Gugelmin | Alain Prost | McLaren-Honda | Report |
| 8 | British Grand Prix | 16 July | Silverstone | Ayrton Senna | Nigel Mansell | Alain Prost | McLaren-Honda | Report |
| 9 | German Grand Prix | 30 July | Hockenheimring | Ayrton Senna | Ayrton Senna | Ayrton Senna | McLaren-Honda | Report |
| 10 | Hungarian Grand Prix | 13 August | Hungaroring | Riccardo Patrese | Nigel Mansell | Nigel Mansell | Ferrari | Report |
| 11 | Belgian Grand Prix | 27 August | Spa-Francorchamps | Ayrton Senna | Alain Prost | Ayrton Senna | McLaren-Honda | Report |
| 12 | Italian Grand Prix | 10 September | Monza | Ayrton Senna | Alain Prost | Alain Prost | McLaren-Honda | Report |
| 13 | Portuguese Grand Prix | 24 September | Estoril | Ayrton Senna | Gerhard Berger | Gerhard Berger | Ferrari | Report |
| 14 | Spanish Grand Prix | 1 October | Jerez | Ayrton Senna | Ayrton Senna | Ayrton Senna | McLaren-Honda | Report |
| 15 | Japanese Grand Prix | 22 October | Suzuka | Ayrton Senna | Alain Prost | Alessandro Nannini | Benetton-Ford | Report |
| 16 | Australian Grand Prix | 5 November | Adelaide | Ayrton Senna | Satoru Nakajima | Thierry Boutsen | Williams-Renault | Report |
Question:
how many times was ayrton senna in pole position?
Answer:
13