import static java.lang.Math.acos;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    }
} import static java.lang.Math.acos; import static java.lang.Math.acos; import static java.lang.Math.acos; import java.math.BigDecimal; BigDecimal java.math import java.math.RoundingMode; RoundingMode java.math import java.text.DecimalFormat; DecimalFormat java.text import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    }
} Main public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    } main {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    } Scanner in=new Scanner(System.in); in new Scanner(System.in) double r=in.nextDouble(); r in.nextDouble() in.nextDouble in double pi=acos(-1.0); pi acos(-1.0) acos -1.0 1.0 Double are=2*pi*r; are 2*pi*r 2*pi*r 2 pi r Double toBeTruncated = new Double(are); toBeTruncated new Double(are) Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue(); truncatedDouble BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue() BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP) BigDecimal.valueOf(toBeTruncated)
    .setScale BigDecimal.valueOf(toBeTruncated) BigDecimal.valueOf BigDecimal toBeTruncated 3 RoundingMode.HALF_UP RoundingMode RoundingMode.HALF_UP System.out.println(toBeTruncated) System.out.println System.out System System.out toBeTruncated String[] args args public class Main {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    }
} Main
import static java.lang.Math.acos;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        double r=in.nextDouble();
        double pi=acos(-1.0);
        Double are=2*pi*r;
        Double toBeTruncated = new Double(are);

Double truncatedDouble = BigDecimal.valueOf(toBeTruncated)
    .setScale(3, RoundingMode.HALF_UP)
    .doubleValue();
        System.out.println(toBeTruncated);
    }
}