Problem:
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

Solution in Go (1.14.1) (judge verdict: Accepted)

package main

import "fmt"

func main() {
	var n, cnt int
	_, _ = fmt.Scan(&n)

	for a := 1; a < n; a++ {
		for b := 1; b <= n-a; b++ {
			if c := n - (a * b); c >= 1 {
				cnt++
			} else {
				break
			}
		}
	}

	fmt.Println(cnt)
}