QOJ.ac

QOJ

Time Limit: 3 s Memory Limit: 512 MB Total points: 100

#7724. 不可约分数

Statistics

给定一个包含 $n$ 个正整数的数组 $a$,求满足以下分数不可约的互不相同的下标四元组 $(i, j, k, l)$ 的数量,即满足 $\gcd(a_i \cdot a_j, a_k \cdot a_l) = 1$ 的四元组数量:

$$\frac{a_i \cdot a_j}{a_k \cdot a_l}$$

第一行包含一个整数 $n$ ($4 \le n \le 2000$),表示数组的长度。第二行包含 $n$ 个整数 $a_i$ ($1 \le a_i \le 10^{12}$),表示数组的元素。

输出一个整数:满足给定条件的四元组数量。

样例

输入格式 1

4
1 1 1 1

输出格式 1

24

输入格式 2

6
10 11 2 4 5 7

输出格式 2

96

Discussions

About Discussions

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.

Open Discussions 0
No discussions in this category.

Issues

About Issues

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:

  1. This is not a place to publish discussions, editorials, or requests to debug your code. Issues are only visible to you and problem moderators.
  2. Do not submit duplicated issues.
  3. Issues must be filed in English or Chinese only.
Active Issues 0
No issues in this category.
Closed/Resolved Issues 0
No issues in this category.