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:
| Party | Leader | From | To |
| --- | --- | --- | --- |
| Scottish National Party | Gordon Wallace | May 1974 | May 1978 |
| Scottish National Party | Robert Cunning | May 1978 | May 1980 |
| Labour | (?) | May 1974 | May 1980 |
| Labour | Iain Nicolson | May 1980 | May 1984 |
| Labour | Charles Kennedy | May 1984 | Jan 1989 |
| Labour | Andrew Cochrane | Jan 1989 | May 1992 |
| Labour | Robert Coyle | May 1992 | May 1993 |
| Labour | Brian Wallace | Jun 1993 | Sep 1994 |
| Labour | Charles Kennedy | Sep 1994 | Apr 1996 |
| Conservative | William Leslie (?) | May 1974 | May 1992 |
| Conservative | Ian Young | May 1992 | April 1996 |
| SDP/Liberal Alliance | Joyce Shannon | February 1986 | May 1992 |
| Independent | Andrew Archibald | May 1974 | May 1977 |
Question:
how many parties had the same leader in office twice?
Answer:
1