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Contest: Task: Related: TaskB TaskD

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