# Task

In the city, a bus named Fibonacci runs on the road every day.

There are `n` stations on the route. The Bus runs from station1 to stationn.

At the departure station(station1), `k` passengers get on the bus. 

At the second station(station2), a certain number of passengers get on and the same number get off. There are still `k` passengers on the bus.

From station3 to stationn-1, the number of boarding and alighting passengers follows the following rule:

- At stationi, the number of people getting on is the sum of the number of people getting on at the two previous stations(stationi-1 and stationi-2)
- The number of people getting off is equal to the number of people getting on at the previous station(stationi-1).

At stationn, all the passengers get off the bus. 

Now, The numbers we know are: `k` passengers get on the bus at station1, `n` stations in total, `m` passengers get off the bus at stationn.

We want to know: How many passengers on the bus when the bus runs out stationx.

# Input

- `k`: The number of passengers get on the bus at station1.
  - `1 <= k <= 100`


- `n`: The total number of stations(1-based).
  - `6 <= n <= 30`


- `m`: The number of passengers get off the bus at stationn.
  - `1 <= m <= 10^10`


- `x`: Stationx(1-based). The station we need to calculate.
  - `3 <= m <= n-1`


- All inputs are valid integers.

# Output

An integer. The number of passengers on the bus when the bus runs out stationx.

```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 = "class Memoize:\n    def __init__(self, fn):\n        self.fn = fn\n        self.memo = {}\n\n    def __call__(self, *args):\n        if args not in self.memo:\n            self.memo[args] = self.fn(*args)\n        return self.memo[args]\n\n@Memoize #makes things alot faster\ndef fib_spec(n): #that is the gain per station, so really we have to take the sum of all n's\n    if n == 0:\n        return (1, 0)\n    elif n == 1:\n        return (0, 1)\n    else:\n        k_1, s_1 = fib_spec(n-1)\n        k_2, s_2 = fib_spec(n-2)\n        return (k_1+k_2, s_1+s_2)\n\n\ndef calc(k,n,m,x):\n    if x in (1,2):\n        return k\n    elif x == 3:\n        return 2*k\n    s_ = 0\n    k_ = 1\n    for i in range(n-3):\n        tmp_k, tmp_s = fib_spec(i)\n        s_ += tmp_s\n        k_ += tmp_k\n        if i == x-3:\n            s_x, k_x = s_, k_\n    s = (m-k*k_)//s_\n    return k_x*k+s_x*s"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'calc'
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: 6220