Cure

Time Limit: 3000/1000 MS (Java/Others)

Memory Limit: 32768/32768 K (Java/Others)

Description

Given an integer $n$, we only want to know the sum of $1/k^2$ where $k$ from $1$ to $n$.

Input

There are multiple cases.
For each test case, there is a single line, containing a single positive integer $n$.
The input file is at most 1M.

Output

The required sum, rounded to the fifth digits after the decimal point.

Sample Input

1 2 4 8 15

Sample Output

1.00000 1.25000 1.42361 1.52742 1.58044

Hint

wange2014

Source

2016 ACM/ICPC Asia Regional Qingdao Online

提交代码