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(input) {
  const n = parseInt(input[0]);
  let cnt=0;
  for(let i=1;i<=(n-1);i++){
    for(let j=1;j<=(n-1);j++){
      if((i*j)<=(n-1)){
        cnt++;
      }
    }
  }
  console.log(cnt);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"));