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.*;


public class Main{
	
	public static void main(String[] args){
	
	MyScanner sc = new MyScanner();
	out = new PrintWriter(new BufferedOutputStream(System.out));
	
	/**/
	
	int number = sc.nextInt();
	long counter = 0;	
		
		
	for(int a = 1; a < number; a++){
		
		for(int b = 1; b < number; b++){
			
			if(number - (a * b) > 0){
				counter++;
			}else{
				break;
			}
			
		}
		
	}	
		
		System.out.println(counter);
		
		
	


	
	
	
	/**/
	 
	 out.close();	
	}
	
	public static PrintWriter out;
	
	public static class MyScanner{
		
		BufferedReader br;
		StringTokenizer st;
		
		public MyScanner(){
			br = new BufferedReader(new InputStreamReader(System.in));
		}
		
		String next() {
          while (st == null || !st.hasMoreElements()) {
              try {
                  st = new StringTokenizer(br.readLine());
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          return st.nextToken();
      }
 
      int nextInt() {
          return Integer.parseInt(next());
      }
 
      long nextLong() {
          return Long.parseLong(next());
      }
 
      double nextDouble() {
          return Double.parseDouble(next());
      }
 
      String nextLine(){
          String str = "";
	  try {
	     str = br.readLine();
	  } catch (IOException e) {
	     e.printStackTrace();
	  }
	  return str;
      }

   }
	
}