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: Wrong Answer)

n = int(input()) - 1

j = 0

ans = 0

for i in range(1, n // 2):
    
    j = i
    
    while True:
        j += 1
        if i * j > n:
            break
        ans += 1

k = 1

er = 0

while True:
    if k ** 2 > n:
        break
    er += 1
    k += 1

print((ans * 2) + er)