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:
| Year | Competition | Venue | Position | Event | Notes |
| --- | --- | --- | --- | --- | --- |
| 2001 | Beijing Marathon | Beijing, PR China | 7th | Marathon | 2:10:46 |
| 2002 | Beijing Marathon | Beijing, PR China | 1st | Marathon | 2:13:09 |
| 2004 | Olympic Games | Athens, Greece | 31st | Marathon | 2:19:26 |
| 2007 | Xiamen International Marathon | Xiamen, PR China | 1st | Marathon | 2:13:17 |
| 2007 | World Championships | Osaka, Japan | 43rd | Marathon | 2:32:44 |
| 2008 | Olympic Games | Beijing, PR China | 51st | Marathon | 2:24:08 |
Question:
how many marathons were held in beijing?
Answer:
3