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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

function spilitInput(input) {
  var splited = [];
  var rows = input.split('\n');
  for (var i = 0; i < rows.length; i += 1) {
    splited.push(rows[i].split(' '));
  }
  return splited;
}
function Main(input) {
  var splited = spilitInput(input);
  var N = splited[0][0];
  
  var counter = 0;
  for (var A = 1; A < N; A += 1) {
  for (var B = 1; (A * B) < N; B += 1) {
    counter += 1;
  }
  }

  console.log(counter);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));