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 Python (3.8.2) (judge verdict: Time Limit Exceeded)

def get_divisors_number(n):
  divisorNumber = 0
  num = 1
  for i in range(N):
    if n % num == 0:
      divisorNumber += 1
    num += 1
    if num ** 2 > n:
      break
  if (num-1) ** 2 == n:
    return divisorNumber * 2 - 1
  return divisorNumber * 2

N = int(input())
result = 0
for i in range(N-1):
  result += get_divisors_number(i+1)
print(result)