Codeforces Beta Round 53
C
Array
Codeforces
1900
原题
← BD →
翻译中…

Chris the Rabbit has been interested in arrays ever since he was a child. At the moment he is researching arrays with the length of $*n*$, containing only integers from $1$ to $*n*$. He is not good at math, that's why some simple things drive him crazy. For example, yesterday he grew keen on counting how many different beautiful arrays there are. Chris thinks that an array is beautiful if it meets one of the two conditions:

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  • each elements, starting from the second one, is no more than the preceding one
  • each element, starting from the second one, is no less than the preceding one
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Having got absolutely mad at himself and at math, Chris came to Stewie and Brian to ask them for help. However, they only laughed at him and said that the answer is too simple and not interesting. Help Chris the Rabbit to find the answer at last.

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Input

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The single line contains an integer $*n*$ which is the size of the array ($1 ≤ *n* ≤ 10^{5}$).

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Output

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You must print the answer on a single line. As it can be rather long, you should print it modulo $1000000007$.

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样例

Input #1
2
Output #1
4
InputCopy OutputCopy
Input #2
3
Output #2
17
InputCopy OutputCopy
题目信息
题号
57C
时间限制
2 s
内存限制
256 MB
标签
组合数学
数学

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