You are given a string S of length N consisting of lowercase English letters.
Process Q queries of the following two types:
 - Type 1: change the i_q-th character of S to c_q. (Do nothing if the i_q-th character is already c_q.)
 - Type 2: answer the number of different characters occurring in the substring of S between the l_q-th and r_q-th characters (inclusive).

-----Constraints-----
 - N, Q, i_q, l_q, and r_q are integers.
 - S is a string consisting of lowercase English letters.
 - c_q is a lowercase English letter.
 - 1 \leq N \leq 500000
 - 1 \leq Q \leq 20000
 - |S| = N
 - 1 \leq i_q \leq N
 - 1 \leq l_q \leq r_q \leq N
 - There is at least one query of type 2 in each testcase.

-----Input-----
Input is given from Standard Input in the following format:
N
S
Q
Query_1
\vdots
Query_Q

Here, Query_i in the 4-th through (Q+3)-th lines is one of the following:
1 i_q c_q

2 l_q r_q

-----Output-----
For each query of type 2, print a line containing the answer.

-----Sample Input-----
7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7

-----Sample Output-----
3
1
5

In the first query, cdbb contains three kinds of letters: b , c , and d, so we print 3.
In the second query, S is modified to abcdzbd.
In the third query, a contains one kind of letter: a, so we print 1.
In the fourth query, S is modified to abcazbd.
In the fifth query, S does not change and is still abcazbd.
In the sixth query, abcazbd contains five kinds of letters: a, b, c, d, and z, so we print 5.

```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

ns = {"__name__": "__main__"}
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'class Segment_tree():\n    def __init__(self, n, s):\n        self.alphabet_list = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]\n        self.key = dict()\n        self.k = 1\n        for value in self.alphabet_list:\n            self.key[value] = self.k\n            self.k *= 2\n        self.inf = pow(2, 32)\n        self.n = n\n        self.s = s\n        self.N = 1\n        while self.N < self.n:\n            self.N *= 2\n        self.size = self.N * 2\n        self.size -= 1\n        self.N -= 1\n        self.segment = [0]*(self.N) + [self.key[self.s[i]] for i in range(self.n)] + [0]*(self.size-self.N-self.n)\n        for i in range(self.N-1, -1, -1):\n            self.segment[i] = self.segment[2*i+1]|self.segment[2*i+2]\n\n    def update(self, i, x):\n        i += (self.N-1)\n        self.segment[i] = self.key[x]\n        while i > 0:\n            i = (i-1)//2\n            self.segment[i] = self.segment[2*i+1]|self.segment[2*i+2]\n        \n    def find(self, a, b, k, l, r):\n        if r <= a or b <= l:\n            return 0\n        elif a <= l and r <= b:\n            return self.segment[k]\n        else:\n            find_l = self.find(a, b, 2*k+1, l, (l+r)//2)\n            find_r = self.find(a, b, 2*k+2, (l+r)//2, r)\n            return find_l|find_r\n\n\nn = int(input())\ns = input()\nsegment = Segment_tree(n, s)\nq = int(input())\nN = 1\nwhile N < n:\n  N *= 2\nfor i in range(q):\n    quer = [x for x in input().split()]\n    if quer[0] == "1":\n        i, c = int(quer[1]), quer[2]\n        segment.update(i, c)\n    else:\n        l, r = int(quer[1]), int(quer[2])\n        key = segment.find(l-1, r, 0, 0, N)\n        ans = 0\n        for i in range(26):\n            if (key>>i)&1:\n                ans += 1\n        print(ans)'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

```

Measured memory_bytes: 16511