Given a positive integer, $n$, find and print the number of pairs of positive integers $(a,b)$, where $a<b$, that exist such that the equation $x\cdot a+y\cdot b=n$ (where $\boldsymbol{x}$ and $y$ are positive integers) has at least one solution.

Input Format

A single positive integer denoting $n$.

Constraints

$4\leq n\leq3\times10^5$

Output Format

Print a single integer denoting the number of such pairs.

Sample Input 0
4

Sample Output 0
2

Explanation 0

There are two such $(a,b)$ pairs: $(1,2)$ and $(1,3)$.

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