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: Time Limit Exceeded)

"use strict";

function main(input) {
  input = Number(input.trim());
  let count = 0;
  for (let c = 1; c <= input; c++) {
    for (let a = 1; a < input; a++) {
      for (let b = 1; b < input; b++) {
        if (a * b + c == input) {
          count++;
        }
      }
    }
  }
  console.log(count);
}

function numberSort(array) {
  array.sort(f);
  return array;
}

var f = function (a, b) {
  return a - b;
};

main(require("fs").readFileSync("/dev/stdin", "utf-8"));