Score : $300$ points

Problem Statement

Given is a positive integer $N$. How many tuples $(A,B,C)$ of positive integers satisfy $A \times B + C = N$?

Constraints

• $2 \leq N \leq 10^6$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$

Output

Print the answer.

3

3

There are $3$ tuples of integers that satisfy $A \times B + C = 3$: $(A, B, C) = (1, 1, 2), (1, 2, 1), (2, 1, 1)$.

100

473

1000000

13969985