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

1. Find a place as far from other people as possible
2. 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

Have fun :)

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'def last_chair(n):\n    # Propn:\n    #   Given there are n seats, n >= 2. The (n-1)th seat is always the\n    #   last to be taken (taken in iteration n).\n    # Proof:\n    #   Suppose that, for some n >= 2, the (n-1)th seat is taken on\n    #   iteration i > 2. The nth seat is already taken, since the 2nd\n    #   iteration will always claim it. Therefore i must sit beside\n    #   at least one person (the occupant of seat n).\n    #   Additionally, the (n-2)th seat must also already be taken.\n    #   If it were not taken, (n-2) would have a free seat at (n-1)\n    #   and would be closer to the exit, and so would rank higher\n    #   than (n-1) in the choice algorithm.\n    #   Therefore (n-1) will only be chosen when (n-2) and (n) are\n    #   both taken.\n    #   Also, all other seats must also be taken, since\n    #   otherwise i would taken them, having at most as many people\n    #   around as seat (n-1) and being closer to the exit.\n    #   Therefore (n-1) is the last seat to be taken.\n    return n - 1'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'last_chair'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 5272