Given a string text, return the number of distinct substrings of text that can be written as the concatenation of a string with itself. More formally, count the number of unique substrings that can be expressed as $a + a$, where $a$ is some string of length greater than $0$.

Constraints:

• $1 \leq$ text.length $\leq 2000$

• text consists of only lowercase English letters.

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Implement your solution in the following coding playground.