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.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;

public class C {
	static Random random;
	private static void mySort(int[] s) {
        for (int i = 0; i < s.length; ++i) {
            int j = random.nextInt(i + 1);
            int t = s[i];
            s[i] = s[j];
            s[j] = t;
        }
        Arrays.sort(s);
    }
	
	static class Pair{
		int x;
		int y;
		
		public Pair(int x, int y) {
			this.x=x;
			this.y=y;
		}
	}
	
	public static void sortPairX(Pair[] p) {
		Arrays.sort(p, new Comparator<Pair>() {
			public int compare(Pair o1, Pair o2) {
				return o1.x-o2.x;
			}			
		});
	}
	
	public static void sortPairY(Pair[] p) {
		Arrays.sort(p, new Comparator<Pair>() {
			public int compare(Pair o1, Pair o2) {
				return o1.y-o2.y;
			}			
		});
	}
	
	
	
	public static void main(String[] args) {
		random = new Random(543534151132L + System.currentTimeMillis());
		InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);


        int nb=in.nextInt();
        int[] T=new int[nb];
        
        T[0]=1;
        int i=1;
        nb--;
        while(nb>=((i+1)+T[i-1])) {
        	T[i]=(i+1)+T[i-1];
        	nb-=T[i];
        	i++;
        }
        out.println(i);
        
        
        
        out.close();
		
	}
	
	
	
	public static int gcd(int a, int b)  
    { 
        BigInteger b1 = BigInteger.valueOf(a); 
        BigInteger b2 = BigInteger.valueOf(b); 
        BigInteger gcd = b1.gcd(b2); 
            return gcd.intValue(); 
    } 
      
    public static long gcd(long a, long b)  
    { 
        BigInteger b1 = BigInteger.valueOf(a); 
        BigInteger b2 = BigInteger.valueOf(b); 
        BigInteger gcd = b1.gcd(b2); 
            return gcd.longValue(); 
    } 
	
	static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }
        
        public long nextLong() {
            return Long.parseLong(next());
        }
        
        public double nextDouble() {
            return Double.parseDouble(next());
        }
        
        public float nextFloat() {
            return Float.parseFloat(next());
        }
        
    }

}