2820: Vanya and Cubes
[Creator : ]
Description
time limit per test
1 secondmemory limit per test
256 megabytesinput
standard inputoutput
standard outputVanya 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:
