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.io.*;
import java.util.*;

public class a {
	BufferedReader br;
	StringTokenizer in;
	PrintWriter out;

	public void solve() throws IOException {
		int n = nextInt() - 1;
		int ans = 1;
		while (n > 0) {
			int s = (ans + 1) * (ans + 2) / 2;
			if (s <= n) {
				ans++;
				n -= s;
			} else {
				n = 0;
			}
		}
		out.println(ans);
	}

	public String nextToken() throws IOException {
		while (in == null || !in.hasMoreTokens()) {
			in = new StringTokenizer(br.readLine());
		}
		return in.nextToken();
	}

	public int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}

	public double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}

	public long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}

	public void run() throws IOException {

		// br = new BufferedReader(new FileReader(new File("")));
		// out = new PrintWriter("");
		br = new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		solve();

		br.close();
		out.close();

	}

	public static void main(String[] args) throws IOException {
		new a().run();

	}
}