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 = "SIDE_LEFT = 'left'\nSIDE_RIGHT = 'right'\nSIDE_TOP = 'top'\nSIDE_BOTTOM = 'bottom'\n\nclass Solution:\n    def isPrintable(self, targetGrid: List[List[int]]) -> bool:\n        \n        # Step 1: Get the set of the different colours being used\n        colour_set = set()\n        for row in targetGrid:\n            for cell in row:\n                colour_set.add(cell)\n        \n        # Step 2: Determine the size of each rectangle and the colours that overlap\n        colour_overlap_info = self.get_colour_boundaries_and_overlap(targetGrid, colour_set)\n        #print(colour_set, colour_overlap_info)\n\n        # Step 3: Loop over the overlapping info. With each pass, print from the last colours downward. In this way, we'll determine\n        # which colours we will print going backwards. If we can't print a colour underneath in an iteration, we've failed\n        remaining_colours = colour_set.copy()\n        untangled_colours = set()\n        while remaining_colours:\n            new_untangled_colours = set()\n            for colour in remaining_colours:\n                # Remove any colours that have been untangled\n                colour_overlap_info[colour] -= untangled_colours\n                if len(colour_overlap_info[colour]) == 0:\n                    # We just untangled this one!\n                    new_untangled_colours.add(colour)\n            \n            # Check if we've untangled anything new. If not, exit\n            #print(new_untangled_colours)\n            if new_untangled_colours:\n                untangled_colours |= new_untangled_colours  # Add them to the full set\n                remaining_colours -= new_untangled_colours  # Remove them from the full list\n            else:\n                break\n        \n        return len(remaining_colours) == 0  # If we've untangled everything, there are no remaining colours and it can be printed\n                    \n        \n    def get_colour_boundaries_and_overlap(self, targetGrid, colour_set):\n        # Determine the size of each rectangle and the colours that overlap\n        colours_info = {}\n        for colour in colour_set:\n            \n            # Get the boundaries\n            boundaries = {}\n            for row_index, row in enumerate(targetGrid):\n                for col_index, cell in enumerate(row):\n                    if cell == colour:\n                        # Update the boundaries\n                        if not boundaries:\n                            # Initialize\n                            boundaries = {\n                                SIDE_LEFT: col_index,\n                                SIDE_RIGHT: col_index,\n                                SIDE_TOP: row_index,\n                                SIDE_BOTTOM: row_index\n                            }\n                        else:\n                            # Update the boundaries. Note that top can't move but left can\n                            if boundaries[SIDE_LEFT] > col_index:\n                                boundaries[SIDE_LEFT] = col_index\n                            if boundaries[SIDE_RIGHT] < col_index:\n                                boundaries[SIDE_RIGHT] = col_index\n                            if boundaries[SIDE_BOTTOM] < row_index:\n                                boundaries[SIDE_BOTTOM] = row_index\n            #print(colour, boundaries)\n            \n            # Now that we have the boundaries, get the colours inside them\n            overlapping_colours = set()\n            for row_index in range(boundaries[SIDE_TOP], boundaries[SIDE_BOTTOM] + 1):\n                for col_index in range(boundaries[SIDE_LEFT], boundaries[SIDE_RIGHT] + 1):\n                    cell = targetGrid[row_index][col_index]\n                    if cell != colour:\n                        overlapping_colours.add(cell)\n            \n            # Save the data\n            colours_info[colour] = overlapping_colours\n        \n        return colours_info\n        \n"
_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: 7844