Solve the programming task below in a Python markdown code block.
Read problem statements in [Hindi], [Bengali], [Mandarin Chinese], [Russian], and [Vietnamese] as well.

For positive integers $a$ and $b$, we say that a fraction $\frac{a}{b}$ is *good* if it is equal to $\frac{m}{m+1}$ for some positive integer $m$.

You are given an integer $N$. Find the number of pairs of integers $i, j$ such that $1 ≤ i, j ≤ N$ and the fraction $\frac{i}{i+1} \cdot \frac{j+1}{j}$ is good.

------  Input ------
The first and only line of the input contains a single integer $N$.

------  Output ------
Print a single line containing one integer ― the number of pairs of integers $i, j$ ($1 ≤ i, j ≤ N$) such that $\frac{i}{i + 1} \cdot \frac{j+1}{j}$ is good.

------  Constraints ------
$1 ≤ N ≤ 1,000,000$

------  Subtasks ------
Subtask #1 (5 points): $1 ≤ N ≤ 2,000$

Subtask #2 (10 points): $1 ≤ N ≤ 100,000$

Subtask #3 (85 points): original constraints

----- Sample Input 1 ------ 
5
----- Sample Output 1 ------ 
8
----- explanation 1 ------ 
The following eight pairs $(i, j)$ give good fractions: $(1,2)$, $(1,3)$, $(2,3)$, $(2,4)$, $(2,5)$, $(3,4)$, $(3,5)$ and $(4,5)$.