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:
| No. | Name | Term of Office | President(s) served under |
| --- | --- | --- | --- |
| 1 | William Bennett | 1989 – 1991 | George H. W. Bush |
| 2 | Bob Martinez | March 28, 1991 - January 20, 1993 | George H. W. Bush |
| 3 | Lee P. Brown | January 1993 – December 12, 1995 | Bill Clinton |
| 4 | Barry McCaffrey | February 29, 1996 – January 4, 2001 | Bill Clinton |
| 5 | John P. Walters | December 7, 2001 – January 19, 2009 | George W. Bush |
| 6 | Gil Kerlikowske | May 7, 2009 – March 6, 2014 | Barack Obama |
| Acting | Michael Botticelli | March 6, 2014 – | Barack Obama |
Question:
how long did bob martinez serve as director?
Answer:
2 years