Problem:
Score : 100 points

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

Solution in Pascal (FPC 3.0.4) (judge verdict: Wrong Answer)

Uses math;
Var n,m,i,a,sum:Longint;
Begin
    Readln(n,m);
    For i:=1 to m do begin
        Read(a);
        sum:=sum+a;
    End;
    Writeln(max(n-sum,-1));
End.