Given a string s, return the last substring of s in lexicographical order.
 
Example 1:
Input: "abab"
Output: "bab"
Explanation: The substrings are ["a", "ab", "aba", "abab", "b", "ba", "bab"]. The lexicographically maximum substring is "bab".

Example 2:
Input: "leetcode"
Output: "tcode"

 
Note:

1 <= s.length <= 4 * 10^5
s contains only 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    # build the suffix tree of the string and traverse the tree by always pick the right most branch.\n    def lastSubstring(self, s: str) -> str:\n        class TreeNode:\n            def __init__(self):\n                self.children = collections.defaultdict()\n\n        # build the suffix tree\n        root = TreeNode()\n        for start in range(len(s)):\n            node = root\n            for c in s[start:]:\n                if c not in node.children:\n                    node.children[c] = TreeNode()\n                node = node.children[c]\n        # traverse the tree\n        res = ''\n        node = root\n        while node and len(node.children) > 0:\n            for i in range(25, -1, -1):  # find the rightmost available branch\n                c = chr(ord('a') + i)\n                if c in node.children:\n                    node = node.children[c]\n                    res += c\n                    break\n        return res\n    \n    # It can be seen that the last substring in lexicographical order is always a suffix of the string.\n    # Start with all possible suffix strings. Each time eliminate the ones not started from the largest letter.\n    # Continue until there is only one distinct letter.\n    def lastSubstring(self, s: str) -> str:\n        i, indexes = 0, list(range(len(s)))\n        while len(indexes) > 1:\n            new = []\n            mx = max([s[i + j] for j in indexes if i + j < len(s)])\n            for k, j in enumerate(indexes):\n                if k - 1 >= 0 and indexes[k - 1] + i == j:\n                    continue\n                if i + j >= len(s):\n                    break\n                if s[i + j] == mx:\n                    new.append(j)\n            i += 1\n            indexes = new\n        return s[indexes[0]:]\n"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'lastSubstring'
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: 6044