A ladder is a set of cubes, in which each of the upper ones
layer contains fewer cubes than the previous one.
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Count the number of ladders that can be built with N cubes.
Input
The input file contains the number N (1<=N<=100).
Output
Output the desired number of ladders into the output file.
Example
Example input file
3
Example output file
2
Запрещенные операторы:for;while;until