3427: Sereja and Subsequences
Description
Sereja has a sequence that consists of n positive integers, a1,a2,...,an.
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=x1,x2,...,xr doesn't exceed a sequence of positive integers y=y1,y2,...,yr, if the following inequation holds: x1≤y1,x2≤y2,...,xr≤yr.
Now Sereja wonders, how many sequences are written on the lines piece of paper. Help Sereja, find the required quantity modulo 1000000007 (109+7).
The first line contains integer n (1≤n≤105). The second line contains n integers a1,a2,...,an (1≤ai≤106).
In the single line print the answer to the problem modulo 1000000007 (109+7).
1
42
42
3
1 2 2
13
5
1 2 3 4 5
719