Problem Statement

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 $10^{-2}$.

Sample Input 1

1

Sample Output 1

6.28318530717958623200

Since we accept an absolute or relative error of at most $10^{-2}$, $6.28$ is also an acceptable output, but $6$ is not.

Sample Input 2

73

Sample Output 2

458.67252742410977361942