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)

function main(lines) {
  const N = n();

  let cnt = 0;
  for (let c = 1; c < N; c++) {
    const _N = N-c;
    const max = Math.sqrt(_N);
    for (let a = 1; a <= max; a++) {
      if (_N % a == 0) {
        if (_N / a == a) cnt++;
        else cnt += 2;
      }
    }
  }
  
  return cnt;
}



const lines = require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n");

let lineCount = 0;
const s = () => lines[lineCount++];
const n = () => Number(s());
const b = () => BigInt(s());
const sa = () => s().split(' ');
const na = () => sa().map(Number);
const ba = () => sa().map(BigInt);
const getLines = (n) => lines.slice(lineCount, lineCount += n);

const ans = main(lines);
console.log( ans );