p02548 AtCoder Beginner Contest 179 - A x B + C
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
```python
N = int(input())
ans = 0
for i in range(1, N):
    ans += (N - 1) // i
print(ans)
```