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.*;
import java.lang.*;
import java.io.*;
class Main
{
    public static int function(int n){
      	int count = 0;
        for(int c = 1; c < n; c++){
          for(int a = 1; a < n; a++){
            for(int b = 1; b < n; b++){
              if(a*b + c == n){
                count++;
                break;
              }
            }
          }
        }
      return count;
    }
    
	public static void main (String[] args) throws java.lang.Exception
	{
	    try{
		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int T= Integer.parseInt(reader.readLine());
        System.out.println(function(T));
	    }
	    catch( Exception e){
	        return ;
	    }
	}
}