Given a string `s`, you can transform every letter individually to be lowercase or uppercase to create another string.

Return a list of all possible strings we could create. Return the output in any order.

Example 1:

    Input: s = "a1b2"
    Output: ["a1b2","a1B2","A1b2","A1B2"]

Example 2:

    Input: s = "3z4"
    Output: ["3z4","3Z4"]

Constraints:

- `1 <= s.length <= 12`
- `s` consists of lowercase English letters, uppercase English letters, and digits.