AtCoder Beginner Contest 206（Sponsored by Panasonic）
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Problem Statement
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Given an array of $N$ integers $A=(A_1,A_2,...,A_N)$, find the number of pairs $(i,j)$ of integers satisfying all of the following conditions:
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$1 \le i < j \le N$$A_i \neq A_j$
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Constraints
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- All values in input are integers.
$2 \le N \le 3 \times 10^5$$1 \le A_i \le 10^9$
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Input
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Input is given from Standard Input in the following format:
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N
A_1 A_2 \dots A_N翻译中…
Output
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Print the answer as an integer.
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样例
Input #1
3
1 7 1
Output #1
2
In this input, we have $A=(1,7,1)$.
- For the pair $(1,2)$, $A_1 \neq A_2$.
- For the pair $(1,3)$, $A_1 = A_3$.
- For the pair $(2,3)$, $A_2 \neq A_3$.
Input #2
10
1 10 100 1000 10000 100000 1000000 10000000 100000000 1000000000
Output #2
45
Input #3
20
7 8 1 1 4 9 9 6 8 2 4 1 1 9 5 5 5 3 6 4
Output #3
173
题目信息
题面与样例版权归 AtCoder 及出题人所有；中文翻译由 AI 生成（CI 管线），如有出入请以原文为准。