如果两个正整数的最大公约数为 $1$，则称它们互质。给定一个正整数序列 $a_{1}, a_{2}, \ldots, a_{n}$，求其中互质的项对的数量。
第一行包含一个整数 $n$ ($1 \le n \le 1\,000\,000$)，表示序列的长度。第二行包含 $n$ 个整数 $a_{i}$ ($1 \le a_{i} \le 3\,000\,000$)。
输出一个整数，表示满足 $1 \le i < j \le n$ 且 $a_{i}$ 与 $a_{j}$ 互质的数对 $(i, j)$ 的数量。
5 3 6 4 7 3
6
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: