给定一个包含 $n$ 个不同正整数的数组 $a$。请找出满足 $1 \le i, j \le n$ 且 $a_i^2 + a_j$ 为完全平方数的数对 $(i, j)$ 的数量。
第一行包含一个整数 $n$ ($1 \le n \le 10^6$)，表示数组的大小。 第二行包含 $n$ 个不同的正整数 $a_1, \dots, a_n$ ($1 \le a_i \le 10^6$)。
输出一个整数：问题的答案。
5 1 2 3 4 5
2
在样例中，有两个这样的数对，分别为 $1^2 + 3 = 4 = 2^2$ 和 $2^2 + 5 = 9 = 3^2$。
| ID | Type | Status | Title | Posted By | Last Updated | Actions |
|---|---|---|---|---|---|---|
| Editorial | Open | Official Editorial | Qingyu | - | Download |
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