You are installing a billboard and want it to have the largest height.  The billboard will have two steel supports, one on each side.  Each steel support must be an equal height.
You have a collection of rods which can be welded together.  For example, if you have rods of lengths 1, 2, and 3, you can weld them together to make a support of length 6.
Return the largest possible height of your billboard installation.  If you cannot support the billboard, return 0.
 
Example 1:
Input: [1,2,3,6]
Output: 6
Explanation: We have two disjoint subsets {1,2,3} and {6}, which have the same sum = 6.


Example 2:
Input: [1,2,3,4,5,6]
Output: 10
Explanation: We have two disjoint subsets {2,3,5} and {4,6}, which have the same sum = 10.



Example 3:
Input: [1,2]
Output: 0
Explanation: The billboard cannot be supported, so we return 0.


 
Note:

0 <= rods.length <= 20
1 <= rods[i] <= 1000
The sum of rods is at most 5000.

```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 = 'class Solution:\n    def tallestBillboard(self, rods: List[int]) -> int:\n        \n        dp = {0: 0}\n        for r in rods:\n            dp2 = dp.copy()\n            for d in list(dp.keys()):\n                dp2[d + r] = max(dp2.get(d + r, 0), dp[d])\n                dp2[abs(d - r)] = max(dp2.get(abs(d - r), 0), dp[d] + min(d, r))\n            dp = dp2\n        # print(dp)\n        return dp[0]\n    \n    \n        # dp = {0: 0}\n        # for x in rods:\n        #     for d, y in dp.items():\n        #         dp[d + x] = max(dp.get(x + d, 0), y)\n        #         dp[abs(d - x)] = max(dp.get(abs(d - x), 0), y + min(d, x))\n        # return dp[0]\n        \n        \n        \n#         @lru_cache(None)\n#         def dp(i, s):\n#             if i == len(rods):\n#                 return 0 if s == 0 else float(\\"-inf\\")\n#             return max(dp(i + 1, s), dp(i + 1, s - rods[i]), dp(i + 1, s + rods[i]) + rods[i])\n        \n#         return dp(0, 0)\n        \n        \n        \n        \n#         dp = {}\n#         dp[0] = 0\n        \n#         for i in rods:\n#             cur = collections.defaultdict(int)\n#             for s in dp:\n#                 cur[s+i] = max(dp[s] + i, cur[s+i])\n#                 cur[s] = max(dp[s], cur[s])\n#                 cur[s-i] = max(dp[s], cur[s-i])\n#             dp = cur\n#         return dp[0]\n'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'tallestBillboard'
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: 6790