Given a string `s` consisting only of characters a, b and c.

Return the number of substrings containing at least one occurrence of all these characters a, b and c.

Example 1:

    Input: s = "abcabc"
    Output: 10
    Explanation: The substrings containing at least one occurrence of the characters a, b and c are "abc", "abca", "abcab", "abcabc", "bca", "bcab", "bcabc", "cab", "cabc" and "abc" (again).

Example 2:

    Input: s = "aaacb"
    Output: 3
    Explanation: The substrings containing at least one occurrence of the characters a, b and c are "aaacb", "aacb" and "acb".

Example 3:

    Input: s = "abc"
    Output: 1

Constraints:

- `3 <= s.length <= 5 x 10^4`
- `s` only consists of a, b or c characters.