101792: [AtCoder]ABC179 C - A x B + C
Memory Limit：256 MB
Time Limit：2 S
Judge Style：Text Compare
Creator：
Submit：0
Solved：0
Description
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.
Sample Input 1
3
Sample Output 1
3
There are $3$ tuples of integers that satisfy $A \times B + C = 3$: $(A, B, C) = (1, 1, 2), (1, 2, 1), (2, 1, 1)$.
Sample Input 2
100
Sample Output 2
473
Sample Input 3
1000000
Sample Output 3
13969985