Given an array arr that represents a permutation of numbers from 1 to n. You have a binary string of size n that initially has all its bits set to zero.
At each step i (assuming both the binary string and arr are 1-indexed) from 1 to n, the bit at position arr[i] is set to 1. You are given an integer m and you need to find the latest step at which there exists a group of ones of length m. A group of ones is a contiguous substring of 1s such that it cannot be extended in either direction.
Return the latest step at which there exists a group of ones of length exactly m. If no such group exists, return -1.
 
Example 1:
Input: arr = [3,5,1,2,4], m = 1
Output: 4
Explanation:
Step 1: "00100", groups: ["1"]
Step 2: "00101", groups: ["1", "1"]
Step 3: "10101", groups: ["1", "1", "1"]
Step 4: "11101", groups: ["111", "1"]
Step 5: "11111", groups: ["11111"]
The latest step at which there exists a group of size 1 is step 4.
Example 2:
Input: arr = [3,1,5,4,2], m = 2
Output: -1
Explanation:
Step 1: "00100", groups: ["1"]
Step 2: "10100", groups: ["1", "1"]
Step 3: "10101", groups: ["1", "1", "1"]
Step 4: "10111", groups: ["1", "111"]
Step 5: "11111", groups: ["11111"]
No group of size 2 exists during any step.

Example 3:
Input: arr = [1], m = 1
Output: 1

Example 4:
Input: arr = [2,1], m = 2
Output: 2

 
Constraints:

n == arr.length
1 <= n <= 10^5
1 <= arr[i] <= n
All integers in arr are distinct.
1 <= m <= arr.length

```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(object):\n#     def findLatestStep(self, arr, m):\n#         \\"\\"\\"\n#         :type arr: List[int]\n#         :type m: int\n#         :rtype: int\n#         \\"\\"\\"\n#         self.rank = collections.defaultdict(int)\n#         self.p = collections.defaultdict(int)\n        \n#         def find(i):\n#             if i not in self.p:\n#                 self.p[i] = i\n#                 self.rank[i] = 1\n#                 return i\n#             p = self.p[i]\n#             while p != self.p[p]:\n#                 p = self.p[p]\n#             self.p[i] = p\n#             return p\n        \n#         def union(i, j):\n#             ip, jp = find(i), find(j)\n#             if ip == jp:\n#                 return False\n#             ir, jr = self.rank[ip], self.rank[jp]\n#             if ir > jr:\n#                 self.p[jp] = ip\n#                 self.rank[ip] += self.rank[jp]\n#                 self.rank.pop(jp)\n#             else:\n#                 self.p[ip] = jp\n#                 self.rank[jp] += self.rank[ip]\n#             return True\n        \n        \n#         status = [0] * len(arr)\n#         res = -1\n#         l = len(arr)\n#         for step, i in enumerate(arr):\n#             i -= 1\n#             status[i] = 1\n#             self.p[i] = i\n#             self.rank[i] = 1\n#             for j in [i-1, i+1]:\n#                 if 0<= j < l:\n#                     if self.rank[find(j)] == m:\n#                         res = step\n#                         print(self.p)\n#                         print(self.rank)\n#                     if status[j] == 1:\n#                         union(i, j)\n                        \n#         for i in range(l):\n#             if self.rank[find(i)] == m:\n#                 return l\n            \n#         return res\n\nclass UnionFindSet:\n    def __init__(self, n):\n        self.parents = list(range(n))\n        self.ranks = [0] * n\n        \n    def find(self, u):\n        if u != self.parents[u]:\n            self.parents[u] = self.find(self.parents[u])\n        return self.parents[u]\n    \n    def union(self, u, v):\n        pu, pv = self.find(u), self.find(v)\n        if pu == pv:\n            return False\n        if self.ranks[pu] > self.ranks[pv]:\n            self.parents[pv] = pu\n            self.ranks[pu] += self.ranks[pv]\n        elif self.ranks[pv] > self.ranks[pu]:\n            self.parents[pu] = pv\n            self.ranks[pv] += self.ranks[pu]\n        else:\n            self.parents[pu] = pv\n            self.ranks[pv] += self.ranks[pu]\n        return True\n\nclass Solution:\n    def findLatestStep(self, arr: List[int], m: int) -> int:\n        n, ans = len(arr), -1\n        uf = UnionFindSet(n)\n        \n        for step, i in enumerate(arr):\n            i -= 1\n            uf.ranks[i] = 1\n            for j in (i - 1, i + 1):\n                if 0 <= j < n:\n                    if uf.ranks[uf.find(j)] == m:\n                        ans = step\n                    if uf.ranks[j]:\n                        uf.union(i, j)\n        \n        for i in range(n):\n            if uf.ranks[uf.find(i)] == m:\n                return n\n            \n        return ans'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'findLatestStep'
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

```

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