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A9001 | Sereja and Subsequences

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题目描述

Sereja has a sequence that consists of $n$ positive integers, $a_{1},a_{2},...,a_{n}$ .

First Sereja took a piece of squared paper and wrote all distinct non-empty non-decreasing subsequences of sequence $a$ . Then for each sequence written on the squared paper, Sereja wrote on a piece of lines paper all sequences that do not exceed it.

A sequence of positive integers $x=x_{1},x_{2},...,x_{r}$ doesn't exceed a sequence of positive integers $y=y_{1},y_{2},...,y_{r}$ , if the following inequation holds: $x_{1}<=y_{1},x_{2}<=y_{2},...,x_{r}<=y_{r}$ .

Now Sereja wonders, how many sequences are written on the lines piece of paper. Help Sereja, find the required quantity modulo $1000000007$ $(10^{9}+7)$ .

输入格式

The first line contains integer $n$ $(1<=n<=10^{5})$ . The second line contains $n$ integers $a_{1},a_{2},...,a_{n}$ $(1<=a_{i}<=10^{6})$ .

输出格式

In the single line print the answer to the problem modulo $1000000007$ $(10^{9}+7)$ .

输入输出样例

输入 #1
1
42
输出 #1
42
输入 #2
3
1 2 2
输出 #2
13
输入 #3
5
1 2 3 4 5
输出 #3
719
C++ 编辑器
输入
输出