A format for expressing an ordered list of integers is to use a comma separated list of either

* individual integers
* or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. The range includes all integers in the interval including both endpoints.  It is not considered a range unless it spans at least 3 numbers. For example "12,13,15-17"

Complete the solution  so that it takes a list of integers in increasing order and returns a correctly formatted string in the range format. 

**Example:**

```python
solution([-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20])
# returns "-6,-3-1,3-5,7-11,14,15,17-20"
```

```C#
RangeExtraction.Extract(new[] {-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20});
# returns "-6,-3-1,3-5,7-11,14,15,17-20"
```

*Courtesy of rosettacode.org*

```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 = 'from typing import List, Tuple\n\n\ndef solution(args: List[int]) -> str:\n    res: str = ""\n    length: int = len(args)\n    idx: int = 0\n\n    while idx < length:\n        if isRange(args, idx):\n            r, inc = showRange(args, idx)\n            res += r\n            idx += inc\n        else:\n            r = showInt(args, idx)  # handles separator\n            res += r\n            idx += 1\n    return res\n\n\ndef isRange(rng: List[int], idx: int) -> bool:\n    # a range spans at least 3 integers\n    if len(rng)-3 < idx:\n        return False\n\n    n: int = rng[idx]\n    nn: int = rng[idx+1]\n    nnn: int = rng[idx+2]\n    if n+1 == nn and nn+1 == nnn:\n        return True\n\n    return False\n\n\ndef showRange(rng: List[int], idx: int) -> Tuple[str, int]:\n    # determine range\n    # determine if range spans until the end (for separator!)\n    curr: int = idx\n    length: int = len(rng)\n    while rng[curr]+1 == rng[curr+1]:\n        curr += 1\n        if (curr+1 == length):\n            break\n\n    res: str = str(rng[idx]) + "-" + str(rng[curr])\n    dist: int = curr - idx + 1\n    assert(dist >= 3)  # implied by the algorithm\n    if not atEnd(rng, curr):\n        res += ","\n\n    return (res, dist)\n\n\ndef showInt(rng: List[int], idx: int) -> str:\n    res: str = str(rng[idx])\n    if atEnd(rng, idx):\n        return res\n    else:\n        return res + ","\n\n\ndef atEnd(lst: List, idx: int) -> bool:\n    return len(lst)-1 == idx'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'solution'
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: 6175