1079\. Letter Tile Possibilities

Medium

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`.

**Example 1:**

**Input:** tiles = "AAB"

**Output:** 8

**Explanation:** The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".

**Example 2:**

**Input:** tiles = "AAABBC"

**Output:** 188

**Example 3:**

**Input:** tiles = "V"

**Output:** 1

**Constraints:**

*   `1 <= tiles.length <= 7`
*   `tiles` consists of uppercase English letters.