There is a strange printer with the following two special requirements:

On each turn, the printer will print a solid rectangular pattern of a single color on the grid. This will cover up the existing colors in the rectangle.
Once the printer has used a color for the above operation, the same color cannot be used again.

You are given a m x n matrix targetGrid, where targetGrid[row][col] is the color in the position (row, col) of the grid.
Return true if it is possible to print the matrix targetGrid, otherwise, return false.
 
Example 1:

Input: targetGrid = [[1,1,1,1],[1,2,2,1],[1,2,2,1],[1,1,1,1]]
Output: true

Example 2:

Input: targetGrid = [[1,1,1,1],[1,1,3,3],[1,1,3,4],[5,5,1,4]]
Output: true

Example 3:
Input: targetGrid = [[1,2,1],[2,1,2],[1,2,1]]
Output: false
Explanation: It is impossible to form targetGrid because it is not allowed to print the same color in different turns.
Example 4:
Input: targetGrid = [[1,1,1],[3,1,3]]
Output: false

 
Constraints:

m == targetGrid.length
n == targetGrid[i].length
1 <= m, n <= 60
1 <= targetGrid[row][col] <= 60

```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 = '# 1591. Strange Printer II\n\ndef walk (grid):\n    for i, row in enumerate (grid):\n        for j, elem in enumerate (row):\n            yield ((i, j), elem)\n\ndef extend (bound, ij):\n    i, j = ij\n    if bound is None:\n        return (ij, ij)\n    else:\n        ((i0, j0), (i1, j1)) = bound\n        return (\n            (min (i0, i), min (j0, j)),\n            (max (i1, i), max (j1, j)),\n        )\n\ndef contains (bound, ij):\n    i, j = ij\n    ((i0, j0), (i1, j1)) = bound\n    return i0 <= i <= i1 and j0 <= j <= j1\n\ndef has_toposort (prereq):\n    roots = [x for x in prereq if not prereq[x]]\n    while roots:\n        r = roots.pop ()\n        del prereq[r]\n        for c in prereq:\n            if r in prereq[c]:\n                prereq[c].remove (r)\n                if not prereq[c]:\n                    roots.append (c)\n    return not prereq\n\ndef printable (grid):\n    m, n = len (grid), len (grid[0])\n    assert m >= 1 and n >= 1\n\n    colors = {c for row in grid for c in row}\n    bounds = {c: None for c in colors}\n\n    for ((i, j), c) in walk (grid):\n        bounds[c] = extend (bounds[c], (i, j))\n\n    prereq = {c: set() for c in colors}\n    for ((i, j), c) in walk (grid):\n        for c2 in colors:\n            if c2 == c: continue\n            if contains (bounds[c2], (i, j)):\n                prereq[c].add (c2)\n\n    return has_toposort (prereq)\n\nclass Solution:\n    def isPrintable(self, targetGrid: List[List[int]]) -> bool:\n        return printable(targetGrid)'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'isPrintable'
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: 8652