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 PyPy3 (7.3.0) (judge verdict: Time Limit Exceeded)

def make_divisors_sum(n):
    divisors_sum = 0
    for i in range(1, int(n**0.5)+1):
        if n % i == 0:
            divisors_sum += 1
            if i != n // i:
              divisors_sum += 1
    return divisors_sum

N = int(input())
sumdiv = 0
for i in range(1,N):
  sumdiv += make_divisors_sum(i)
print(sumdiv)