import java.math.BigDecimal;
import java.math.MathContext;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		BigDecimal n = BigDecimal.valueOf(sc.nextDouble());
		sc.close();
		System.out.println(func(n));
	}

	public static BigDecimal func(BigDecimal n) {
		BigDecimal x = n.divide(BigDecimal.valueOf(3), MathContext.DECIMAL32);

		return x.multiply(x).multiply(x);
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz