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:
| Name | Class | Navy | Date joined | Date departed |
| --- | --- | --- | --- | --- |
| HMS Bluebell | Flower class corvette | Royal Navy | 18 October | 21 October |
| HMCS Elk | Armed yacht | Royal Canadian Navy | 5 October | 7 October |
| HMS Fowey | Shoreham class sloop | Royal Navy | 18 October | 21 October |
| HMS Heartsease | Flower class corvette | Royal Navy | 18 October | 21 October |
| HMS Leith | Grimsby class sloop | Royal Navy | 18 October | 21 October |
| HMS Scarborough | Hastings class sloop | Royal Navy | 5 October | 21 October |
Question:
What's the departed date that the HMS Leith of the Royal Navy?
Answer:
21 October