There's a waiting room with N chairs set in single row. Chairs are consecutively numbered from 1 to N. First is closest to the entrance (which is exit as well).
For some reason people choose a chair in the following way
- Find a place as far from other people as possible
- Find a place as close to exit as possible
All chairs must be occupied before the first person will be served
So it looks like this for 10 chairs and 10 patients
| Chairs | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Patients | 1 | 7 | 5 | 8 | 3 | 9 | 4 | 6 | 10 | 2 |
Your task is to find last patient's chair's number.
Input - N - integer greater than 2 - number of chairs. Output should positive integer too - last patient's chair's number