Return the number of distinct non-empty substrings of `text` that can be written as the concatenation of some string with itself (i.e. it can be written as `a + a` where `a` is some string).

Example 1:

    Input: text = "abcabcabc"
    Output: 3
    Explanation: The 3 substrings are "abcabc", "bcabca" and "cabcab".

Example 2:

    Input: text = "leetcodeleetcode"
    Output: 2
    Explanation: The 2 substrings are "ee" and "leetcodeleetcode".

Constraints:

- `1 <= text.length <= 2000`
- `text` has only lowercase English letters.