import java.io.*;

public class ListCubes {
	public static void main(String[] args) throws IOException {
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		double res = 0.0;
		reader.readLine();
		String[] parts = reader.readLine().split(" ");
		for (String s : parts) res += Math.pow(Double.valueOf(s), 3.0);
		System.out.println(Math.pow(res, 0.333333333));
	}
}