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: Accepted)

import java.io.*;
import java.util.*;
class Main
{
	 public static void  main (String[] args) throws IOException
    {
       try{
       BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
       int a=0;
       a=Integer.parseInt(br.readLine());
       long sum=0;int c=1;
       for(int i=1;i<=a;i++)
       {
       	sum+=(a-1)/i;
       }
       System.out.println(sum);
   }
    catch(Exception e){}
}}