You are given a string containing only 4 kinds of characters 'Q', 'W', 'E' and 'R'.
A string is said to be balanced if each of its characters appears n/4 times where n is the length of the string.
Return the minimum length of the substring that can be replaced with any other string of the same length to make the original string s balanced.
Return 0 if the string is already balanced.
 
Example 1:
Input: s = "QWER"
Output: 0
Explanation: s is already balanced.
Example 2:
Input: s = "QQWE"
Output: 1
Explanation: We need to replace a 'Q' to 'R', so that "RQWE" (or "QRWE") is balanced.

Example 3:
Input: s = "QQQW"
Output: 2
Explanation: We can replace the first "QQ" to "ER". 

Example 4:
Input: s = "QQQQ"
Output: 3
Explanation: We can replace the last 3 'Q' to make s = "QWER".

 
Constraints:

1 <= s.length <= 10^5
s.length is a multiple of 4
s contains only 'Q', 'W', 'E' and 'R'.

```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 balancedString(self, s: str) -> int:\n        # minimum window so that outside is possible\n        if len(s) //4 != len(s) / 4: return -1 \n        ans, p1, p2, n_cnt = len(s), 0, 0, collections.Counter(s)\n\n        while p1 < len(s): \n            n_cnt[s[p1]] -= 1     \n            while p2 < len(s) and all(len(s) / 4 >= n_cnt[c] for c in 'QWER'): \n                ans = min(ans, abs(p1 - p2 + 1))\n                n_cnt[s[p2]] += 1\n                p2 += 1\n            if p2 > p1: \n                p1, p2 = p2, p1\n            p1 +=1\n        return ans\n    \n    def balancedString(self, s: str) -> int:\n        # minimum window so that outside is possible\n        if len(s) //4 != len(s) / 4: return -1 \n        ans, p1, p2, n_cnt = len(s), 0, 0, collections.Counter(s)\n\n        while p1 < len(s): \n            n_cnt[s[p1]] -= 1     \n            while p2 < min(p1+2, len(s)) and all(len(s) / 4 >= n_cnt[c] for c in 'QWER'): \n                ans = min(ans, abs(p1 - p2 + 1))\n                n_cnt[s[p2]] += 1\n                p2 += 1\n            # if p2 > p1: \n            #     p1, p2 = p2, p1\n            p1 +=1\n        return ans\n                \n            \n            \n        \n            \n            \n"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'balancedString'
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: 5980