import java.util.*;
import java.math.*;

public class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  }
} import java.util.*; util.* java import java.math.*; math.* java public class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  }
} Main public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  } main {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int S=sc.nextInt(); S sc.nextInt() sc.nextInt sc BigDecimal bd = new BigDecimal((double)S/3); bd new BigDecimal((double)S/3) bd = bd.setScale(8, RoundingMode.HALF_UP) bd bd.setScale(8, RoundingMode.HALF_UP) bd.setScale bd 8 RoundingMode.HALF_UP RoundingMode RoundingMode.HALF_UP BigDecimal s = bd.multiply(bd); s bd.multiply(bd) bd.multiply bd bd BigDecimal v = s.multiply(bd); v s.multiply(bd) s.multiply s bd v = v.setScale(8, RoundingMode.HALF_UP) v v.setScale(8, RoundingMode.HALF_UP) v.setScale v 8 RoundingMode.HALF_UP RoundingMode RoundingMode.HALF_UP System.out.println(v) System.out.println System.out System System.out v String args[] args public class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  }
} public class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  }
} Main
import java.util.*;
import java.math.*;

public class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);
    int S=sc.nextInt();
    BigDecimal bd = new BigDecimal((double)S/3);
    bd = bd.setScale(8, RoundingMode.HALF_UP);
    BigDecimal s = bd.multiply(bd);
    BigDecimal v = s.multiply(bd);
    v = v.setScale(8, RoundingMode.HALF_UP);
    System.out.println(v);
  }
}