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>
#/usr/bin/python

def vanya_and_cube(n):
	i,total,total_blocks=0,0,0
        if(n==0):
             return n

	elif(n<0):
	     return 0
       	
	elif(n==1):
	    return 1

        else:
	    i=1		
	    while(total_blocks <= n):
	          total=total + i
                  total_blocks=total_blocks + total
		  if(total_blocks > n): 	         	
                          return (i-1)
                  i+=1      		  
  
	return (i-1)

 
def main():
    n=int(input())
    ans=vanya_and_cube(n)
    print ans


main()
