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:
| # | Menteri Besar | Took office | Left office | Party |
| --- | --- | --- | --- | --- |
| 1 | Jaafar Mohamed | 1886 | July 1890 | No party |
| 2 | Mohamed Mahbob | June 1920 | 1922 | No party |
| 3 | Abdullah Jaafar | September 1923 | 1928 | No party |
| 4 | Mustapha Jaafar | September 16, 1928 | November 23, 1931 | No party |
| 5 | Abdul Hamid Yusof | November 23, 1931 | December 28, 1934 | No party |
| 6 | Ungku Abdul Aziz Abdul Majid | April 1935 | June 1, 1947 | No party |
| 7 | Onn Jaafar | June 1, 1947 | May 18, 1950 | No party |
| 8 | Syed Abdul Kadir Mohamed | February 18, 1952 | June 5, 1955 | No party |
| 9 | Wan Idris Ibrahim | October 1, 1955 | August 31, 1957 | No party |
Question:
what is the number of menteri besars that there have been during the pre-independence period?
Answer:
9