Given a string array `words`, return an array of all characters that show up in all strings within the `words` (including duplicates). You may return the answer in any order.

Example 1:

    Input: words = ["bella","label","roller"]
    Output: ["e","l","l"]

Example 2:

    Input: words = ["cool","lock","cook"]
    Output: ["c","o"]

Constraints:

- `1 <= words.length <= 100`
- `1 <= words[i].length <= 100`
- `words[i]` consists of lowercase English letters.