5319: ABC163——Task A：Circle Pond
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Description
Print the circumference of a circle of radius RR.
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
$1≤R≤100$
All values in input are integers.
All values in input are integers.
Sample 1 Input
1
Sample 1 Output
6.28318530717958623200
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 2 Input
73
Sample 2 Output
458.67252742410977361942