Format any integer provided into a string with "," (commas) in the correct places.

**Example:**
``` csharp
Kata.NumberFormat(100000); // return "100,000"
Kata.NumberFormat(5678545); // return "5,678,545"
Kata.NumberFormat(-420902); // return "-420,902"
```
``` javascript
numberFormat(100000); // return '100,000'
numberFormat(5678545); // return '5,678,545'
numberFormat(-420902); // return '-420,902'
```
``` cpp
numberFormat(100000); // return '100,000'
numberFormat(5678545); // return '5,678,545'
numberFormat(-420902); // return '-420,902'
```
``` python
number_format(100000); # return '100,000'
number_format(5678545); # return '5,678,545'
number_format(-420902); # return '-420,902'
```
``` ruby
number_format(100000); # return '100,000'
number_format(5678545); # return '5,678,545'
number_format(-420902); # return '-420,902'
```
``` crystal
number_format(100000); # return '100,000'
number_format(5678545); # return '5,678,545'
number_format(-420902); # return '-420,902'
```

```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 = 'import re\ndef number_format(n):\n    # converts int to str, reverses it for next step\n    n = str(n)[::-1]\n    \n    # split into groups of 3 digits\n    g = re.split(r\'(\\d{3})\', n)\n    \n    # remove empty string from list\n    g = list(filter(None, g))\n    \n    # special case where "-" is only char in a group and messes up with ",".join()\n    if g[-1] == "-":\n        return g[-1] + \',\'.join(g[:-1])[::-1]\n    return \',\'.join(g)[::-1]'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'number_format'
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: 36909