The letter value of a letter is its position in the alphabet starting from 0 (i.e. `'a' -> 0`, `'b' -> 1`, `'c' -> 2`, etc.).

The numerical value of some string of lowercase English letters `s` is the concatenation of the letter values of each letter in `s`, which is then converted into an integer.

- For example, if `s = "acb"`, we concatenate each letter's letter value, resulting in `"021"`. After converting it, we get `21`.

You are given three strings `firstWord`, `secondWord`, and `targetWord`, each consisting of lowercase English letters `'a'` through `'j'` inclusive.

Return `true` if the summation of the numerical values of `firstWord` and `secondWord` equals the numerical value of `targetWord`, or `false` otherwise.

Example 1:

    Input: firstWord = "acb", secondWord = "cba", targetWord = "cdb"
    Output: true
    Explanation:
    The numerical value of firstWord is "acb" -> "021" -> 21.
    The numerical value of secondWord is "cba" -> "210" -> 210.
    The numerical value of targetWord is "cdb" -> "231" -> 231.
    We return true because 21 + 210 == 231.

Example 2:

    Input: firstWord = "aaa", secondWord = "a", targetWord = "aab"
    Output: false
    Explanation:
    The numerical value of firstWord is "aaa" -> "000" -> 0.
    The numerical value of secondWord is "a" -> "0" -> 0.
    The numerical value of targetWord is "aab" -> "001" -> 1.
    We return false because 0 + 0 != 1.

Example 3:

    Input: firstWord = "aaa", secondWord = "a", targetWord = "aaaa"
    Output: true
    Explanation:
    The numerical value of firstWord is "aaa" -> "000" -> 0.
    The numerical value of secondWord is "a" -> "0" -> 0.
    The numerical value of targetWord is "aaaa" -> "0000" -> 0.
    We return true because 0 + 0 == 0.

Constraints:

- `1 <= firstWord.length,` `secondWord.length,` `targetWord.length <= 8`
- `firstWord`, `secondWord`, and `targetWord` consist of lowercase English letters from `'a'` to `'j'` inclusive.