|#|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