题目描述
How many infinite sequences a_1, a_2, ... consisting of {{1, ... ,n}} satisfy the following conditions?
- The n-th and subsequent elements are all equal. That is, if $n \leq i,j, a_i = a_j$.
- For every integer i, the a_i elements immediately following the i-th element are all equal. That is, if $i < j < k\leq i+a_i, a_j = a_k$.
Find the count modulo 10^9+7.
Constraints
- $1 \leq n \leq 10^6$
Input
Input is given from Standard Input in the following format:
n
Output
Print how many sequences satisfy the conditions, modulo 10^9+7.
Examples
Input
2
Output
4
Input
654321
Output
968545283
输入格式
见题面
输出格式
见题面
样例输入
654321
样例输出
968545283