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.

Examples

Input

3

Output

3

Input

100

Output

473

Input

1000000

Output

13969985

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