## Story

There are four warriors, they need to go through a dark tunnel. Tunnel is very narrow, every time only can let two warriors through, and there are lot of dangerous traps. Fortunately, they have a lamp that can illuminate the tunnel to avoid being trapped by the trap.

In order to pass this tunnel, they need five steps:

1. Two people go through the tunnel with the lamp
2. And then one people come back with the lamp
3. And then two people go through the tunnel with the lamp
4. And then one people come back with the lamp
5. And then two people go through the tunnel with the lamp
 
Each warrior has his own walking speed, we need to calculate the shortest time they have to cross the tunnel.
 
For example:
 
Four warriors is `a,b,c,d`. Their speed are `[3,4,5,6]`. It means they need 3 minutes, 4 minutes, 5 minutes and 6 minutes to cross the tunnel. The shortest crossing time should be 21 minutes, the method is as follows:
 
```
a and b go through the tunnel  ---> Spend 4 minutes
(Time spent should be calculated by the person who is slow)
a come back                    ---> Spend 3 minutes
a and c go through the tunnel  ---> Spend 5 minutes
a come back                    ---> Spend 3 minutes
a and d go through the tunnel  ---> Spend 6 minutes
```
Do you have any other better way?
 
## Task
Complete function `shortestTime()` that accepts 1 argument: `speed` that are the spent time of four warriors. Returns the shortest time that all warriors go through the tunnel.
 
**Note: The method in example above is not always the best way.**

## Example

```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 math import inf\nfrom itertools import chain, combinations, combinations_with_replacement\n\n# thanks to "The capacity-C torch problem" by Roland Backhouse, Hai Truong\n# https://www.sciencedirect.com/science/article/pii/S0167642315000118\n\ndef shortest_time(speed: [int]):\n    forward_trips_num = 3       # for len(speed) == 4\n    best_time = inf\n#     path = []\n    for forward_trips in combinations_with_replacement(list(combinations(speed, 2)), forward_trips_num):\n        # not all people made at least one forward trip\n        if any(list(chain(*forward_trips)).count(s) < speed.count(s) for s in set(speed)):\n            continue\n        sum_forward = sum([max(trip[0], trip[1]) for trip in forward_trips])     # time of all forward trips\n        sum_return = 0                                                           # time of all return trips\n        # number of return trips for each speed\n        # (if there are several people with equal speed, the sum of all their return trips);\n        returns = {s: 0 for s in set(speed)}\n        for s in set(speed):\n            # for every person the number of forward trips is one more than the number of return trips\n            returns[s] += sum([trip.count(s) for trip in forward_trips]) - speed.count(s)\n            sum_return += returns[s]*s\n\n        if best_time > sum_forward+sum_return:\n            best_time = sum_forward + sum_return\n#             path = list(forward_trips) + list(chain(*[[(s,)]*returns[s] for s in set(speed)]))\n#     print(path)\n    return best_time'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'shortest_time'
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: 12360