P9148 Division Problem.

Given a set $a$ of size $n$, all elements are guaranteed to be distinct and are all positive integers. If we pick three elements $a, b, c$ from it **in order**, then there are $n \cdot (n-1) \cdot (n-2)$ different ways to choose. Now for one choice $(a,b,c)$, define its weight as $\Bigl\lfloor\dfrac{a}{b}\Bigr\rfloor\Bigl\lfloor\dfrac{a}{c}\Bigr\rfloor\Bigl\lfloor\dfrac{b}{c}\Bigr\rfloor$. You need to compute the sum of weights over all choices. You only need to output this sum modulo $2^{32}$. Note: $\lfloor a\rfloor$ denotes the greatest integer not greater than $a$. For example, $\lfloor 2.4\rfloor=2$ and $\lfloor 5\rfloor=5$.

The first line contains a positive integer $n$, the length of the sequence. The second line contains $n$ positive integers $a_1, a_2, \ldots, a_n$. Each number describes one element of the set $a$, and all these numbers are distinct.

Output one line with one integer, the answer modulo $2^{32}$.

**[Sample Explanation #1]** For sample #1, the only choices with non-zero weight are: - $(3,2,1)$, with weight $6$. - $(4,2,1)$, with weight $16$. - $(4,3,1)$, with weight $12$. - $(4,3,2)$, with weight $2$. Therefore, the answer for sample #1 is $6+16+12+2=36$. --- **[Constraints]** For $100\%$ of the testdata, $1 \le n, a_i \le 5000$. **This problem uses bundled tests.** |Subtask|$n$|Special Property|Points| |-|-|-|-| |1|$=3$||$10$| |2|$\le 300$||$20$| |3|$\le 2000$||$20$| |4||A|$20$| |5|||$30$| Special Property A: it is guaranteed that $a_i=i$. --- **[Hint]** In this problem, most algorithms have small constant factors. Please trust your time complexity. Translated by ChatGPT 5