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Description

A positive integer is called a "smart number" if it can be expressed as the difference of squares of two positive integers. For example, $16$ equals $5^2 - 3^2$, so $16$ is a smart number. In the sequence of natural numbers starting from $1$, we number the "smart numbers" in ascending order as $1$, $2$, $3$, ..., $n$. Given a positive integer $n$, output the $n$-th "smart number".

Input Format

The input contains a single positive integer $n$ ($1≤n≤100$).

Output Format

Output a single positive integer representing the $n$-th "smart number".

Sample

3

7