A sentence consists of lowercase letters (`'a'` to `'z'`), digits (`'0'` to `'9'`), hyphens (`'-'`), punctuation marks (`'!'`, `'.'`, and `','`), and spaces (`' '`) only. Each sentence can be broken down into one or more tokens separated by one or more spaces `' '`.

A token is a valid word if all three of the following are true:

- It only contains lowercase letters, hyphens, and/or punctuation (no digits).
- There is at most one hyphen `'-'`. If present, it must be surrounded by lowercase characters (`"a-b"` is valid, but `"-ab"` and `"ab-"` are not valid).
- There is at most one punctuation mark. If present, it must be at the end of the token (`"ab,"`, `"cd!"`, and `"."` are valid, but `"a!b"` and `"c.,"` are not valid).

Examples of valid words include `"a-b."`, `"afad"`, `"ba-c"`, `"a!"`, and `"!"`.

Given a string `sentence`, return the number of valid words in `sentence`.

Example 1:

    Input: sentence = "cat and  dog"
    Output: 3
    Explanation: The valid words in the sentence are "cat", "and", and "dog".

Example 2:

    Input: sentence = "!this  1-s b8d!"
    Output: 0
    Explanation: There are no valid words in the sentence.
    "!this" is invalid because it starts with a punctuation mark.
    "1-s" and "b8d" are invalid because they contain digits.

Example 3:

    Input: sentence = "alice and  bob are playing stone-game10"
    Output: 5
    Explanation: The valid words in the sentence are "alice", "and", "bob", "are", and "playing".
    "stone-game10" is invalid because it contains digits.

Constraints:

- `1 <= sentence.length <= 1000`
- `sentence` only contains lowercase English letters, digits, `' '`, `'-'`, `'!'`, `'.'`, and `','`.
- There will be at least `1` token.