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

-----Sample Output-----
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.

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