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 Java (OpenJDK 11.0.6) (judge verdict: Time Limit Exceeded)

import java.util.Scanner;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int N = sc.nextInt();

        int k=0;
        
        int x;
        
        int c;
        c=0;
        
        for(int i=0;i<N-1;i++) {
        	c=c+1;
        	for(int j=1;j<N-c+1;j++) {
        		x=(N-c)%j;
        		if(x==0) {
        			k=k+1;
        		}
        	}
        }
        
        // 出力
        System.out.println(k);
    }
}