Please solve the programming task below using a self-contained code snippet in a markdown code block.

You have n  tiles, where each tile has one letter tiles[i] printed on it.
Return the number of possible non-empty sequences of letters you can make using the letters printed on those tiles.
 
Please complete the following python code precisely:
```python
class Solution:
    def numTilePossibilities(self, tiles: str) -> int:
```