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 (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	numT := scanner.Text()
	num, _ := strconv.ParseInt(numT, 10, 64)
	n := int(num)
	c := 0
	j := 0

	for i := 1; i <= n; i++ {
		target := n - i

		for j = 1; j <= target; j++ {
			k := target / j
			if j > k {
				break
			}
			if k*j == target {
				c += 2
				if j == k {
					c -= 1
				}
			}
		}
	}

	fmt.Println(c)
}