Problem Statement

Print the circumference of a circle of radius R.

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}.

Constraints

• $1 \leq R \leq 100$
• All values in input are integers.

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

见题面 Input 部分

见题面 Output 部分