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>
n=int(input())
a=[0]*10000
a[0]=1
aa=[1]*10000
sum=1
ans=0
for i in range(10000):
    a[i]=i+1+a[i-1]
    sum+=a[i]
#    if n>=sum and n<sum+a[i]:
#        ans=i
#        break
for i in range(1,10000):  
    aa[i]=a[i]+ aa[i-1]   

#print(a)
#print(aa)
for i in range(10000):
    
   if n>=aa[i] and n<aa[i+1]:
       ans=i
    
print(ans+1)     
    