A string is good if there are no repeated characters.

Given a string `s`​​​​​, return the number of good substrings of length three in `s`​​​​​​.

Note that if there are multiple occurrences of the same substring, every occurrence should be counted.

A substring is a contiguous sequence of characters in a string.

Example 1:

    Input: s = "xyzzaz"
    Output: 1
    Explanation: There are 4 substrings of size 3: "xyz", "yzz", "zza", and "zaz".
    The only good substring of length 3 is "xyz".

Example 2:

    Input: s = "aababcabc"
    Output: 4
    Explanation: There are 7 substrings of size 3: "aab", "aba", "bab", "abc", "bca", "cab", and "abc".
    The good substrings are "abc", "bca", "cab", and "abc".

Constraints:

- `1 <= s.length <= 100`
- `s`​​​​​​ consists of lowercase English letters.