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: Time Limit Exceeded)

package main

import (
	"fmt"
)

func main() {
	var n int

	fmt.Scanf("%d", &n)

	total := 0
	var a, b, c, tmp int
	for a = 1; a < n; a++ {
		for b = 1; b < n; b++ {
			tmp = a * b
			for c = n - tmp; c >= 1; c-- {
				if tmp+c == n {
					total++
				}
			}
		}
	}
	fmt.Println(total)
}