9649: ABC179 —— C - A x B + C
[Creator : ]
Description
Given is a positive integer $N$. How many tuples $(A,B,C)$ of positive integers satisfy $A \times B + C = N$?
Input
Input is given from Standard Input in the following format:
```
$N$
```
```
$N$
```
Output
Print the answer.
Constraints
- $ 2 \leq N \leq 10^6$
- All values in input are integers.
- All values in input are integers.
Sample 1 Input
3
Sample 1 Output
3
There are 33 tuples of integers that satisfy A×B+C=3: (A,B,C)=(1,1,2),(1,2,1),(2,1,1).
Sample 2 Input
100
Sample 2 Output
473
Sample 3 Input
1000000
Sample 3 Output
13969985