Problems
A * B + C
A * B + C
Positive integer $n$ is given. How many tuples $(A, B, C)$ of positive integers satisfy $A \cdot B + C = n$?
\InputFile
One positive integer $n~(2 \le n \le 10^8)$.
\OutputFile
Print the required number of tuples.
\Note
For $n = 3$ there are exactly three triplets:
\begin{itemize}
\item $(1, 1, 2)$, since $1 \cdot 1 + 2 = 3$;
\item $(1, 2, 1)$, since $1 \cdot 2 + 1 = 3$;
\item $(2, 1, 1)$, since $2 \cdot 1 + 1 = 3$.
\end{itemize}
Input example #1
3
Output example #1
3
Input example #2
11
Output example #2
27