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:\n    def findLatestStep(self, arr: List[int], m: int) -> int:\n        if m==1 and len(arr)==1: return(1)\n        if m>len(arr):return(-1)\n        Bins=[0]*len(arr)\n        Gs={}#start,len\n        Ge={}#end,start ix\n        Res=-1\n        Rescnt=0\n        for y in range(len(arr)):\n            i=arr[y]-1\n            if (i==0 or Bins[i-1]==0) and (i==len(arr)-1 or Bins[i+1]==0):\n                #new group\n                # Gl[i]=1\n                # Gs[i]=i\n                Gs.update({i:1})\n                Ge.update({i:i})\n                Bins[i]=1\n                # ix=len(Gs)-1 \n                if m==1:\n                    Res=y+1\n                    Rescnt=Rescnt+1\n                    # print(Res,Rescnt)\n            else:\n                if (i==0 or Bins[i-1]==0) and (i<len(arr)-1 and Bins[i+1]==1):\n                    #extend left i+1\n                    # ix=[k for k,j in enumerate(Gs) if j[0]==(i+1)][0]\n                    Gs.update({i:Gs[i+1]+1})\n                    Ge[Gs[i+1] + i] = i\n                    tmp=Gs.pop(i+1)\n                    # tmpe=Ge.pop(i+1)\n                    Bins[i]=1\n                    if Gs[i]==m:\n                        Res=y+1\n                        Rescnt=Rescnt+1\n                    else: \n                        if tmp==m: Rescnt-=1\n                else:\n                    if (i>0 and Bins[i-1]==1) and (i==len(arr)-1 or Bins[i+1]==0):\n                        #extend right i-1\n                        # strt=i-1\n                        # while(strt>0 and Bins[strt]==1):strt-=1\n                        # if(Bins[strt]==0):strt+=1\n                        \n                        # ix=[k for k in Gs.keys() if k+Gs[k]==i][0]\n                        # ix=[k for k,j in enumerate(Gs) if j[0]==strt][0]\n                        ix=Ge[i-1]\n                        tmp=Gs[ix]\n                        Gs[ix]=Gs[ix]+1 \n                        tmpe=Ge.pop(i-1)\n                        Ge.update({i:ix})\n                        Bins[i]=1\n                        # if(Gs[ix][1]==m):Res=i\n                        if Gs[ix]==m:\n                            Res=y+1\n                            Rescnt=Rescnt+1\n                        else: \n                            if tmp==m: Rescnt-=1\n                    else:\n                        if (i>0 and Bins[i-1]==1) and (i<len(arr)-1 and Bins[i+1]==1):\n                            #merge Len=Sum+1\n\n                            # ix=[k for k in Gs.keys() if k+Gs[k]==i][0]\n                            # print('merge',i)\n                            ix=Ge[i-1]\n                            # print('ix',ix,i)\n                            tmp0=Gs[ix]\n                            Gs[ix]=Gs[ix]+Gs[i+1]+1\n                            tmp=Gs.pop(i+1)\n                            tmpe=Ge.pop(i-1)\n                            # print('ix2',tmp+i)\n                            Ge[tmp+i]=ix\n                            Bins[i]=1\n                            if Gs[ix]==m:\n                                Res=y+1\n                                Rescnt=Rescnt+1\n                            else: \n                                if tmp==m: Rescnt-=1\n                                if tmp0==m: Rescnt-=1                                \n            if Rescnt>0: Res=y+1\n            # print(i,'E',Ge)\n            # print('S',Gs)\n            \n            # for r in range(len(Gs)):\n            #         if Gs[r][1]==m:\n            #             Res=y+1\n            #             break                    \n        return(Res)"
_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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