class Main{public static void main(String[]a){System.out.print(6.28*new java.util.Scanner(System.in).nextInt());}} class Main{public static void main(String[]a){System.out.print(6.28*new java.util.Scanner(System.in).nextInt());}} Main public static void main(String[]a){System.out.print(6.28*new java.util.Scanner(System.in).nextInt());} main {System.out.print(6.28*new java.util.Scanner(System.in).nextInt());} System.out.print(6.28*new java.util.Scanner(System.in).nextInt()) System.out.print System.out System System.out 6.28*new java.util.Scanner(System.in).nextInt() 6.28 new java.util.Scanner(System.in).nextInt() new java.util.Scanner(System.in).nextInt new java.util.Scanner(System.in) String[]a a
class Main{public static void main(String[]a){System.out.print(6.28*new java.util.Scanner(System.in).nextInt());}}