Created by Antoine Mazières

You must provide the function `draw_n_squares(n)`

that **returns** a string of squares, such as:

```
>>> from solution import draw_n_squares
>>> print(draw_n_squares(1))
+---+
| |
+---+
>>> print(draw_n_squares(3))
+---+---+---+
| | | |
+---+---+---+
| | | |
+---+---+---+
| | | |
+---+---+---+
>>> print(draw_n_squares(5))
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
| | | | | |
+---+---+---+---+---+
```

`n`

is the number of squares on the diagonal.