You've made it through the moat and up the steps of knowledge. You've won the temples games and now you're hunting for treasure in the final temple run. There's good news and bad news. You've found the treasure but you've triggered a nasty trap. You'll surely perish in the temple chamber.

With your last movements, you've decided to draw an "X" marks the spot for the next archeologist.

Given an odd number, n, draw an X for the next crew. Follow the example below.

`
`
If n = 1 return 'X\n' and if you're given an even number or invalid input, return '?'.

The output should be a string with no spaces after the final X on each line, but a \n to indicate a new line.


Check out my other 80's Kids Katas:


80's Kids #1: How Many Licks Does It Take
80's Kids #2: Help Alf Find His Spaceship
80's Kids #3: Punky Brewster's Socks
80's Kids #4: Legends of the Hidden Temple
80's Kids #5: You Can't Do That on Television
80's Kids #6: Rock 'Em, Sock 'Em Robots
80's Kids #7: She's a Small Wonder
80's Kids #8: The Secret World of Alex Mack
80's Kids #9: Down in Fraggle Rock 
80's Kids #10: Captain Planet

```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 = 'def mark_spot(n):\n    if not isinstance(n, int) or not n%2 or n<1: return \'?\'\n\n    spots = [[\' \']*n for _ in range(n)]\n    for i,row in enumerate(spots):\n        row[i],row[-1-i] = \'XX\'\n\n    return \'\\n\'.join( \' \'.join(row).rstrip() for row in spots+[""] )'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'mark_spot'
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: 7096