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>
/*
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 * and open the template in the editor.
 */

import java.io.IOException;
import static java.lang.System.in;
import java.lang.reflect.Array;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import static java.util.Collections.list;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.IntStream;


/**
 *
 * @author george
 */
public class main {
public static boolean isPrime(long n) {
    if(n < 2) return false;
    if(n == 2 || n == 3) return true;
    if(n%2 == 0 || n%3 == 0) return false;
    long sqrtN = (long)Math.sqrt(n)+1;
    for(long i = 6L; i <= sqrtN; i += 6) {
        if(n%(i-1) == 0 || n%(i+1) == 0) return false;
    }
    return true;
}

static public class Princess{
 public int rate;public int beauty;public int intellect;public int richness;
 public Princess(int sum,int a,int b,int c){
  this.rate=sum;
  this.beauty=a;
  this.intellect=b;
  this.richness=c;
  }

        @Override
        public String toString() {
            return "Princess{" + "rate=" + rate + ", beauty=" + beauty + ", intellect=" + intellect + ", richness=" + richness + '}';
        }
 
 }
public static boolean contains(final int[] arr, final int key) {
    return Arrays.stream(arr).anyMatch(i -> i == key);
}
 static boolean isSubSequence(String str1, String str2, int m, int n)
    {
       
        if (m == 0) 
            return true;
        if (n == 0) 
            return false;
             
        
        if (str1.charAt(m-1) == str2.charAt(n-1))
            return isSubSequence(str1, str2, m-1, n-1);
 
        
        return isSubSequence(str1, str2, m, n-1);
    }

    static int gcdThing(int a, int b) {
    BigInteger b1 = BigInteger.valueOf(a);
    BigInteger b2 = BigInteger.valueOf(b);
    BigInteger gcd = b1.gcd(b2);
    return gcd.intValue();
}
    public static boolean checkAnagram(String str1, String str2) {
        int i=0;
        for (char c : str1.toCharArray()) {
        i = str2.indexOf(c, i) + 1;
        if (i <= 0) { return false; }
    }
    return true;

}
    /* Amusing Joke 
    String a,b,c;
     a=s.next();b=s.next();c=s.next();
     if((a.length()+b.length())!=c.length()){System.out.print("here");System.out.print("NO");}
     else{
         boolean x= true;
         String agex="";
         if(checkAnagram(a, c)==false){System.out.print("here1");x=false;}
         else{
             char [] g=a.toCharArray();
             Arrays.sort(g);String ge=new String(g);a=ge;
             g=b.toCharArray();Arrays.sort(g);ge=new String(b);b=ge;
             g=c.toCharArray();Arrays.sort(g);ge=new String(c);c=ge;
            if(isSubSequence(a, c, a.length(), c.length())){
                 StringBuilder sb = new StringBuilder(c);String temp="";
                for (int i = 0; i < a.length(); i++) {
                    temp+=a.charAt(i);
                 c.replaceFirst(temp, "");temp="";
                   
                }
            }
            else{x=false;}
            if(isSubSequence(a, c, a.length(), c.length())){
              StringBuilder sb = new StringBuilder(c);
                for (int i = 0; i < b.length(); i++) {
                  String temp="";
                    temp+=b.charAt(i);
                 c.replaceFirst(temp, "");temp="";
                   
                }
            }
            else{x=false;}
            if(c.length()!=0){x=false;}
    }if(x==false){System.out.print("NO");}
    else{System.out.print("YES");}
    }
    */
   public static void main (String []  args) throws IOException 
    {
      Scanner s=new Scanner(System.in);
      long n=s.nextInt();
      int i=0;
      int sum=0;
      int total=0;
      while(n-total>0){
      i++;
      sum+=i;total+=sum;if(total>n){i--;break;}
      }
      if(total==n){System.out.print(i);}
      else{System.out.print(i--);}
     
       }
      }
    
        
        
   
      
    

    


   

