bobo 热爱等比数列！所以他想知道序列 $a_1, a_2, \dots, a_n$ 中长度为 3 的等比数列的个数。 也就是说，计算满足 $i < j < k$ 且 $a_i \cdot a_k = a_j^2$ 的三元组 $(i, j, k)$ 的数量。
第一行包含一个整数 $n$ ($1 \le n \le 1000000$)。 第二行包含 $n$ 个整数 $a_1, a_2, \dots, a_n$ ($1 \le a_1 < a_2 < \dots < a_n \le 1000000$)。
输出一个整数，表示等比数列的个数。
3 1 2 4
1
4 1 2 4 8
2
The discussion section is only for posting: General Discussions (problem-solving strategies, alternative approaches), and Off-topic conversations.
This is NOT for reporting issues! If you want to report bugs or errors, please use the Issues section below.
If you find any issues with the problem (statement, scoring, time/memory limits, test cases, etc.), you may submit an issue here. A problem moderator will review your issue.
Guidelines: