Vanya got n cubes. He decided to build a pyramid from them. Vanya wants to build the pyramid as follows: the top level of the pyramid must consist of 1 cube, the second level must consist of 1 + 2 = 3 cubes, the third level must have 1 + 2 + 3 = 6 cubes, and so on. Thus, the i-th level of the pyramid must have 1 + 2 + ... + (i - 1) + i cubes.

Vanya wants to know what is the maximum height of the pyramid that he can make using the given cubes.

Input

The first line contains integer n (1 ≤ n ≤ 104) — the number of cubes given to Vanya.

Output

Print the maximum possible height of the pyramid in the single line.

Examples

Input

1


Output

1


Input

25


Output

4

Note

Illustration to the second sample: 

<image>
import java.util.Scanner;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author mthai
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		Scanner in = new Scanner(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		VanyaAndCubes solver = new VanyaAndCubes();
		solver.solve(1, in, out);
		out.close();
	}
}

class VanyaAndCubes {
    public int N;

    public void solve(int testNumber, Scanner in, PrintWriter out) {
        N = in.nextInt();

        out.println(dp());
    }

    public int dp() {
        int []memo = new int[N];
        memo[0] = 1;
        for(int i = 1; i < N; ++i) {
            int total = ((i + 1) * ((i + 1) + 1)) / 2;
            memo[i] += total + memo[i - 1];
            if(memo[i] > N) {
                return i;
            }
        }
        return 1;
    }
}
