import java.io.*;

public class Main {

  static boolean checkKaibun(String str){
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  }

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  }
} import java.io.*; io.* java public class Main {

  static boolean checkKaibun(String str){
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  }

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  }
} Main static boolean checkKaibun(String str){
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  } checkKaibun {
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  } StringBuilder t = new StringBuilder(str); t new StringBuilder(str) return (str.equals(t.reverse().toString())); (str.equals(t.reverse().toString())) str.equals str t.reverse().toString() t.reverse().toString t.reverse() t.reverse t String str str public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  } main {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String[] in; in in = br.readLine().split(" ") in br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double l = Double.parseDouble(in[0]); l Double.parseDouble(in[0]) Double.parseDouble Double in[0] in 0 br.close() br.close br System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0))) System.out.println System.out System System.out String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)) String.format String "%.10f" (l / 3.0) * (l / 3.0) * (l / 3.0) (l / 3.0) * (l / 3.0) * (l / 3.0) (l / 3.0) l 3.0 (l / 3.0) l 3.0 (l / 3.0) l 3.0 String[] args args public class Main {

  static boolean checkKaibun(String str){
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  }

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  }
} public class Main {

  static boolean checkKaibun(String str){
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  }

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  }
} Main
import java.io.*;

public class Main {

  static boolean checkKaibun(String str){
    StringBuilder t = new StringBuilder(str);
    return (str.equals(t.reverse().toString()));
  }

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
    String[] in;
    in = br.readLine().split(" ");
    double l = Double.parseDouble(in[0]);

    br.close();

    System.out.println(String.format("%.10f", (l / 3.0) * (l / 3.0) * (l / 3.0)));
    
  }
}