# Task
 Smartphones software security has become a growing concern related to mobile telephony. It is particularly important as it relates to the security of available personal information.
 
 For this reason, Ahmed decided to encrypt phone numbers of contacts in such a way that nobody can decrypt them. At first he tried encryption algorithms very complex, but the decryption process is tedious, especially when he needed to dial a speed dial.

 He eventually found the algorithm following: instead of writing the number itself, Ahmed multiplied by 10, then adds the result to the original number.
 
 For example, if the phone number is `123`, after the transformation, it becomes `1353`. Ahmed truncates the result (from the left), so it has as many digits as the original phone number. In this example Ahmed wrote `353` instead of `123` in his smart phone.

 Ahmed needs a program to recover the original phone number from number stored on his phone. The program return "impossible" if the initial number can not be calculated.
 
 Note: There is no left leading zero in either the input or the output; Input `s` is given by string format, because it may be very huge ;-)

# Example

 For `s="353"`, the result should be `"123"`
 
 ```
    1230
  +  123
  .......
  = 1353  
  
  truncates the result to 3 digit -->"353"
  
  So the initial number is "123"
 ```
 For `s="123456"`, the result should be `"738496"`
 
 ```
    7384960
  +  738496
  .........
  = 8123456
  
  truncates the result to 6 digit -->"123456"
  
  So the initial number is "738496"
 ```
 For `s="4334"`, the result should be `"impossible"`
 
 Because no such a number can be encrypted to `"4334"`.

# Input/Output


 - `[input]` string `s`

  string presentation of n with `1 <= n <= 10^100`


 - `[output]` a string

  The original phone number before encryption, or `"impossible"` if the initial number can not be calculated.

```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 decrypt(s):\n    prev, c, r = 0, 0, []\n    for x in reversed(s):\n        d = int(x) - c - prev\n        if d < 0:\n            d += 10\n            c = 1\n        else:\n            c = 0\n        r.append(str(d))\n        prev = d\n    return 'impossible' if not prev else ''.join(r[::-1])"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'decrypt'
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: 5632