In recreational mathematics, a [Keith number](https://en.wikipedia.org/wiki/Keith_number) or repfigit number (short for repetitive Fibonacci-like digit) is a number in the following integer sequence:

`14, 19, 28, 47, 61, 75, 197, 742, 1104, 1537, 2208, 2580, 3684, 4788, 7385, 7647, 7909, ...` (sequence A007629 in the OEIS)

Keith numbers were introduced by Mike Keith in 1987. They are computationally very challenging to find, with only about 100 known.

Implement the code to check if the given number is a Keith number. Return the number number of iteration needed to confirm it; otherwise return `false`.

**Note:** 1-digit numbers are **not** Keith numbers by definition


## Examples

```
n = 197      # --> [1, 9, 7]

# calculation           iteration
1 + 9 + 7 = 17         #    1
9 + 7 + 17 = 33        #    2
7 + 17 + 33 = 57       #    3
17 + 33 + 57 = 107     #    4
33 + 57 + 107 = 197    #    5
```
As `197` is the same as the initial number, so it's a Keith number: return `5`


Another example:
```
n = 196

# calculation          iteration
1 + 9 + 6 = 16        #    1
...
```

`196` is not a Keith number, so return `false`

```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 = "# It's nice to put the OEIS but it's not that interesting if they give the algo\ndef is_keith_number(n):\n    if n < 10: return False\n    x = list(map(int, str(n)))\n    y, i = sum(x), 1\n    while y < n:\n        i, x, y = i+1, x[1:]+[y], 2*y-x[0]\n    return i * (y==n)"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'is_keith_number'
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: 5730