题目描述
Print the circumference of a circle of radius R.
Constraints
- $1 \leq R \leq 100$
- All values in input are integers.
Input
Input is given from Standard Input in the following format:
R
Output
Print the circumference of the circle. Your output is considered correct if and only if its absolute or relative error from our answer is at most 10^{-2}.
Examples
Input
1
Output
6.28318530717958623200
Input
73
Output
458.67252742410977361942
输入格式
见题面
输出格式
见题面
样例输入
73
样例输出
458.67252742410977361942