CF492A.Vanya and Cubes

普及/提高-

通过率：0%

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题目描述

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.

输入格式

The first line contains integer $n$ ( $1<=n<=10^{4}$ ) — the number of cubes given to Vanya.

输出格式

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

输入输出样例

输入#1
```
1
```
输出#1
```
1
```
输入#2
```
25
```
输出#2
```
4
```

说明/提示

Illustration to the second sample:

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