题库练习 Scalar Queries
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A12614 | Scalar Queries

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内存限制256MB
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题目描述

You are given an array $a_1, a_2, \dots, a_n$ . All $a_i$ are pairwise distinct.

Let's define function $f(l, r)$ as follows:

- let's define array $b_1, b_2, \dots, b_{r - l + 1}$ , where $b_i = a_{l - 1 + i}$ ;
- sort array $b$ in increasing order;
- result of the function $f(l, r)$ is $\sum\limits_{i = 1}^{r - l + 1}{b_i \cdot i}$ .

Calculate $\left(\sum\limits_{1 \le l \le r \le n}{f(l, r)}\right) \mod (10^9+7)$ , i.e. total sum of $f$ for all subsegments of $a$ modulo $10^9+7$ .

输入格式

The first line contains one integer $n$ ( $1 \le n \le 5 \cdot 10^5$ ) — the length of array $a$ .

The second line contains $n$ integers $a_1, a_2, \dots, a_n$ ( $1 \le a_i \le 10^9$ , $a_i \neq a_j$ for $i \neq j$ ) — array $a$ .

输出格式

Print one integer — the total sum of $f$ for all subsegments of $a$ modulo $10^9+7$

输入输出样例

输入 #1
4
5 2 4 7
输出 #1
167
输入 #2
3
123456789 214365879 987654321
输出 #2
582491518
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