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-----
3

-----Sample Output-----
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).

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