Ways to Make Rectangles

Sanggeun has $n$ unit squares, each with side length $1$. Using these squares, how many different rectangles can he make in total?

A rectangle must be filled completely with unit squares, and a square may not be deformed or stacked on top of another. So a rectangle that is $a$ squares wide and $b$ squares tall needs $a \times b$ squares, and since he owns $n$ squares it must satisfy $a \times b \le n$.

Two rectangles are considered the same if one can be turned into the other by moving or rotating it. In other words, an $a \times b$ rectangle and a $b \times a$ rectangle are the same rectangle.

The first line contains an integer $n$. ($1 \le n \le 10000$)

Print the number of different rectangles that can be made.

When $n = 6$, the rectangles that can be made are $1 \times 1$, $1 \times 2$, $1 \times 3$, $1 \times 4$, $1 \times 5$, $1 \times 6$, $2 \times 2$, and $2 \times 3$, for a total of $8$.