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.

The first line contains integer n (1 ≤ n ≤ 104) — the number of cubes given to Vanya.

Print the maximum possible height of the pyramid in the single line.

Illustration to the second sample:

水题、

#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

typedef long long ll;

typedef pair<int,int> pii;

const int INF = 1e9;

const double eps = 1e-;

int cas = ;

int main()

{

    #ifdef LOCAL

//    freopen("case.txt","r",stdin);

    #endif

    int n,ans,sum,sum2;

    while(cin>>n)

    {

        ans = sum = sum2 = ;

        while(true)

        {

            if(sum2 > n) break;

            ans ++ ;

            sum += ans;

            sum2 += sum;

        }

        cout << ans- << endl;

    }

    return ;

}