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:
| Outcome | No. | Date | Championship | Surface | Opponent in the final | Score in the final |
| --- | --- | --- | --- | --- | --- | --- |
| Winner | 1. | 20 July 1981 | Båstad, Sweden | Clay | Anders Järryd | 6–2, 6–3 |
| Runner-up | 1. | 21 September 1981 | Bordeaux, France | Clay | Andrés Gómez | 6–7, 6–7, 1–6 |
| Winner | 2. | 10 June 1985 | Bologna, Italy | Clay | Claudio Panatta | 6–2, 6–0 |
| Winner | 3. | 9 September 1985 | Palermo, Italy | Clay | Joakim Nyström | 6–2, 6–0 |
| Winner | 4. | 23 September 1985 | Barcelona, Spain | Clay | Mats Wilander | 0–6, 6–2, 3–6, 6–4, 6–0 |
| Winner | 5. | 10 February 1986 | Metz, France | Indoor | Broderick Dyke | 6–4, 6–3 |
| Runner-up | 2. | 28 April 1986 | Indianapolis, U.S. | Clay | Andrés Gómez | 4–6, 6–7(1–7) |
| Runner-up | 3. | 28 July 1986 | Washington, D.C., U.S. | Clay | Karel Nováček | 1–6, 6–7(4–7) |
| Runner-up | 4. | 8 September 1986 | Geneva, Switzerland | Clay | Henri Leconte | 5–7, 3–6 |
Question:
which surface was used the least?
Answer:
Indoor