In this Kata, you will be given a string of numbers in sequence and your task will be to return the missing number. If there is no number
missing or there is an error in the sequence, return `-1`.

For example:
```Haskell
missing("123567") = 4 
missing("899091939495") = 92
missing("9899101102") = 100
missing("599600601602") = -1 -- no number missing
missing("8990919395") = -1 -- error in sequence. Both 92 and 94 missing.
```
The sequence will always be in ascending order.

More examples in the test cases. 

Good luck!

```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 = '\nclass State:\n\n    def __init__(self, pos, missing_candidate, expected1, expected2):\n        self.pos = pos\n        self.missing_candidate = missing_candidate\n        self.expected1 = expected1\n        self.expected2 = expected2\n        self.valid = None\n        \n    def update_found_seq(self):\n        self.pos += len(str(self.expected1))\n        self.expected1 += 1\n        self.expected2 = self.expected1 + 1\n    \n    def update_found_skip(self):\n        self.missing_candidate = self.expected1\n        self.pos += len(str(self.expected2))\n        self.expected1 = self.expected2 + 1\n        self.expected2 = self.expected1 + 1\n\n    def __str__(self):\n        return "State({0}, {1}, {2}, {3})".format(self.pos, self.missing_candidate, self.expected1, self.expected2)\n\ndef missing(s):\n    res = -1\n    for l in range(1, len(s)//3+1):\n        q = State(0, None, int(s[0:l]), 0)\n        while q.pos < len(s) and q.valid==None:\n            if s[q.pos:].startswith(str(q.expected1)):\n                q.update_found_seq()\n            elif not q.missing_candidate and s[q.pos:].startswith(str(q.expected2)):\n                q.update_found_skip()\n            else:\n                q.valid = False\n            if q.pos == len(s):\n                q.valid = True\n        if q.valid:\n            if q.missing_candidate:\n                res = q.missing_candidate\n            else:\n                res = -1\n            break\n\n    return res\n'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'missing'
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: 6562