Given two strings str1 and str2, return the shortest string that has both str1 and str2 as subsequences.  If multiple answers exist, you may return any of them.
(A string S is a subsequence of string T if deleting some number of characters from T (possibly 0, and the characters are chosen anywhere from T) results in the string S.)
 
Example 1:
Input: str1 = "abac", str2 = "cab"
Output: "cabac"
Explanation: 
str1 = "abac" is a subsequence of "cabac" because we can delete the first "c".
str2 = "cab" is a subsequence of "cabac" because we can delete the last "ac".
The answer provided is the shortest such string that satisfies these properties.

 
Note:

1 <= str1.length, str2.length <= 1000
str1 and str2 consist of lowercase English letters.

```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 shortestCommonSupersequence(self, str1: str, str2: str) -> str:\n        table = [[[0, -1] for j in range(len(str2))] for i in range(len(str1))]\n        if str1[0] == str2[0]:\n            table[0][0][0] = 1\n        else:\n            table[0][0][0] = 2\n            table[0][0][1] = 0\n        for j in range(1, len(str2)):\n            if str1[0] == str2[j]:\n                table[0][j][0] = j + 1\n                table[0][j][1] = j - 1\n            else:\n                val1, val2 = j + 1, table[0][j-1][0]\n                if val1 < val2:\n                    table[0][j][0] = val1 + 1\n                    table[0][j][1] = j\n                else:\n                    table[0][j][0] = val2 + 1\n                    table[0][j][1] = j - 1\n        for i in range(1, len(str1)):\n            if str1[i] == str2[0]:\n                table[i][0][0] = i + 1\n            else:\n                val1, val2 = table[i-1][0][0], i + 1\n                if val1 < val2:\n                    table[i][0][0] = val1 + 1\n                    table[i][0][1] = 0\n                else:\n                    table[i][0][0] = i + 2\n            for j in range(1, len(str2)):\n                if str1[i] == str2[j]:\n                    table[i][j][0] = table[i-1][j-1][0] + 1\n                    table[i][j][1] = j - 1\n                else:\n                    val1, val2 = table[i-1][j][0], table[i][j-1][0]\n                    if val1 < val2:\n                        table[i][j][0] = val1 + 1\n                        table[i][j][1] = j\n                    else:\n                        table[i][j][0] = val2 + 1\n                        table[i][j][1] = j - 1\n        # for j in range(len(str2)):\n        #     table[-1][j] += len(str2) - 1 - j        \n        # print(table)\n        result = ''\n        pos1, pos2 = len(str1) - 1, len(str2) - 1\n        while True:\n            if str1[pos1] == str2[pos2]:\n                result = str1[pos1] + result\n                pos1, pos2 = pos1 - 1, table[pos1][pos2][1]\n            else:\n                if table[pos1][pos2][1] == pos2:\n                    result = str1[pos1] + result\n                    pos1 -= 1\n                else:\n                    result = str2[pos2] + result\n                    pos2 = table[pos1][pos2][1]\n            # print(pos1, pos2)  \n            if pos1 < 0 or pos2 < 0:\n                result = str1[0:pos1+1] + str2[0:pos2+1] + result\n                break               \n            \n        return result                "
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'shortestCommonSupersequence'
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: 10544