Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

import math
#from math import gcd
import bisect
import heapq
from collections import defaultdict
from collections import deque
from collections import Counter
from functools import lru_cache

#############
# Constants #
#############

MOD = 10**9+7
INF = float('inf')
AZ = "abcdefghijklmnopqrstuvwxyz"

#############
# Functions #
#############

######INPUT######
def I(): return int(input().strip())
def S(): return input().strip()
def IL(): return list(map(int,input().split()))
def SL(): return list(map(str,input().split()))
def ILs(n): return list(int(input()) for _ in range(n))
def SLs(n): return list(input().strip() for _ in range(n))
def ILL(n): return [list(map(int, input().split())) for _ in range(n)]
def SLL(n): return [list(map(str, input().split())) for _ in range(n)]

######OUTPUT######
def P(arg): print(arg); return
def Y(): print("Yes"); return
def N(): print("No"); return
def E(): exit()
def PE(arg): print(arg); exit()
def YE(): print("Yes"); exit()
def NE(): print("No"); exit()

#####Shorten#####
def DD(arg): return defaultdict(arg)

#####Inverse#####
def inv(n): return pow(n, MOD-2, MOD)

######Combination######
kaijo_memo = []
def kaijo(n):
  if(len(kaijo_memo) > n): return kaijo_memo[n]
  if(len(kaijo_memo) == 0): kaijo_memo.append(1)
  while(len(kaijo_memo) <= n): kaijo_memo.append(kaijo_memo[-1] * len(kaijo_memo) % MOD)
  return kaijo_memo[n]

gyaku_kaijo_memo = []
def gyaku_kaijo(n):
  if(len(gyaku_kaijo_memo) > n): return gyaku_kaijo_memo[n]
  if(len(gyaku_kaijo_memo) == 0): gyaku_kaijo_memo.append(1)
  while(len(gyaku_kaijo_memo) <= n): gyaku_kaijo_memo.append(gyaku_kaijo_memo[-1] * pow(len(gyaku_kaijo_memo),MOD-2,MOD) % MOD)
  return gyaku_kaijo_memo[n]

def nCr(n,r):
  if n == r: return 1
  if n < r or r < 0: return 0
  ret = 1
  ret = ret * kaijo(n) % MOD
  ret = ret * gyaku_kaijo(r) % MOD
  ret = ret * gyaku_kaijo(n-r) % MOD
  return ret

######Factorization######
def factorization(n):
  arr = []
  temp = n
  for i in range(2, int(-(-n**0.5//1))+1):
    if temp%i==0:
      cnt=0
      while temp%i==0: 
        cnt+=1 
        temp //= i
      arr.append([i, cnt])
  if temp!=1: arr.append([temp, 1])
  if arr==[]: arr.append([n, 1])
  return arr

#####MakeDivisors######
def make_divisors(n):
  divisors = []
  for i in range(1, int(n**0.5)+1):
    if n % i == 0:
      divisors.append(i)
      if i != n // i: 
        divisors.append(n//i)
  return divisors

#####MakePrimes######
def make_primes(N):
  max = int(math.sqrt(N))
  seachList = [i for i in range(2,N+1)]
  primeNum = []
  while seachList[0] <= max:
    primeNum.append(seachList[0])
    tmp = seachList[0]
    seachList = [i for i in seachList if i % tmp != 0]
  primeNum.extend(seachList)
  return primeNum

#####GCD#####
def gcd(a, b):
    while b: a, b = b, a % b
    return a

#####LCM#####
def lcm(a, b):
    return a * b // gcd (a, b)

#####BitCount#####
def count_bit(n):
  count = 0
  while n:
    n &= n-1
    count += 1
  return count

#####ChangeBase#####
def base_10_to_n(X, n):
  if X//n: return base_10_to_n(X//n, n)+[X%n]
  return [X%n]

def base_n_to_10(X, n):
  return sum(int(str(X)[-i-1])*n**i for i in range(len(str(X))))

def base_10_to_n_without_0(X, n):
  X -= 1
  if X//n: return base_10_to_n_without_0(X//n, n)+[X%n]
  return [X%n]

#####IntLog#####
def int_log(n, a):
  count = 0
  while n>=a:
    n //= a
    count += 1
  return count

#############
# Main Code #
#############
class BIT:
  def __init__(self, logn):
    self.n = 1<<logn
    self.data = [0]*(self.n+1)
    self.el = [0]*(self.n+1)
  def sum(self, i):
    s = 0
    while i > 0:
      s += self.data[i]
      i -= i & -i
    return s
  def add(self, i, x):
    # assert i > 0
    self.el[i] += x
    while i <= self.n:
      self.data[i] += x
      i += i & -i
  def get(self, i, j=None):
    if j is None:
      return self.el[i]
    return self.sum(j) - self.sum(i)
  def bisect(self, x):
    w = i = 0
    k = self.n
    while k:
      if i+k <= self.n and w + self.data[i+k] <= x:
        w += self.data[i+k]
        i += k
      k >>= 1
    return i+1

N = I()
A = list(S())
Q = I()

dic = {l:BIT(int_log(N,2)+1) for l in AZ}

for i in range(N):
  s = A[i]
  dic[s].add(i+1,1)

def change(i,y):
  prev = A[i]
  if prev == y:
    pass
  else:
    A[i] = y
    dic[prev].add(i,-1)
    dic[y].add(i,1)
  
def count(x,y):
  ret = 0
  for l in AZ:
    if dic[l].sum(x-1) != dic[l].sum(y):
      ret += 1
  print(ret)

for _ in range(Q):
  t,x,y = SL()
  if t == "1":
    change(int(x),y)
  else:
    count(int(x),int(y))

Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    bag[S[a-1]].remove(a)
    S[a-1] = b
    bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)


Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    bag[S[a-1]].remove(a)
    S[a-1] = b
    bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[0 for i in range(N)] for l in alphabet}

for i in range(N):
  bag[S[i]][i] = 1

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    bag[S[a-1]][a-1] = 0
    S[a-1] = b
    bag[b][a-1] = 1
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if sum(bag[l][a-1:b]) > 0:
        count += 1
    print(count)


Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    bag[S[a-1]].remove(a)
    S[a-1] = b
    bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      left = bisect.bisect_left(bag[l],a)
      right = bisect.bisect_right(bag[l],b)
      if left !=  right:
        count += 1
    print(count)

Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

import math
from collections import deque
from fractions import gcd
from functools import lru_cache


#############
# Constants #
#############

MOD = 10**9+7
INF = float('inf')

#############
# Functions #
#############

######INPUT######
def inputI(): return int(input().strip())
def inputS(): return input().strip()
def inputIL(): return list(map(int,input().split()))
def inputSL(): return list(map(str,input().split()))
def inputILs(n): return list(int(input()) for _ in range(n))
def inputSLs(n): return list(input().strip() for _ in range(n))
def inputILL(n): return [list(map(int, input().split())) for _ in range(n)]
def inputSLL(n): return [list(map(str, input().split())) for _ in range(n)]

#####Inverse#####
def inv(n): return pow(n, MOD-2, MOD)

######Combination######
kaijo_memo = []
def kaijo(n):
  if(len(kaijo_memo) > n):
    return kaijo_memo[n]
  if(len(kaijo_memo) == 0):
    kaijo_memo.append(1)
  while(len(kaijo_memo) <= n):
    kaijo_memo.append(kaijo_memo[-1] * len(kaijo_memo) % MOD)
  return kaijo_memo[n]

gyaku_kaijo_memo = []
def gyaku_kaijo(n):
  if(len(gyaku_kaijo_memo) > n):
    return gyaku_kaijo_memo[n]
  if(len(gyaku_kaijo_memo) == 0):
    gyaku_kaijo_memo.append(1)
  while(len(gyaku_kaijo_memo) <= n):
    gyaku_kaijo_memo.append(gyaku_kaijo_memo[-1] * pow(len(gyaku_kaijo_memo),MOD-2,MOD) % MOD)
  return gyaku_kaijo_memo[n]

def nCr(n,r):
  if(n == r):
    return 1
  if(n < r or r < 0):
    return 0
  ret = 1
  ret = ret * kaijo(n) % MOD
  ret = ret * gyaku_kaijo(r) % MOD
  ret = ret * gyaku_kaijo(n-r) % MOD
  return ret

######Factorization######
def factorization(n):
    arr = []
    temp = n
    for i in range(2, int(-(-n**0.5//1))+1):
        if temp%i==0:
            cnt=0
            while temp%i==0:
                cnt+=1
                temp //= i
            arr.append([i, cnt])
    if temp!=1:
        arr.append([temp, 1])

    if arr==[]:
        arr.append([n, 1])
    return arr

#####LCM#####
def lcm(a, b):
    return a * b // gcd (a, b)

#############
# Main Code #
#############

N = inputI()
S = list(inputS())
Q = inputI()
Qs = inputSLL(Q)

alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for t,a,b in Qs:
  a = int(a)
  if int(t) == 1:
    bag[S[a-1]].remove(a)
    S[a-1] = b
    bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      left = bisect.bisect_left(bag[l],a)
      right = bisect.bisect_right(bag[l],b)
      if left !=  right:
        count += 1
    print(count)


Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

import math
from collections import deque
from fractions import gcd
from functools import lru_cache


#############
# Constants #
#############

MOD = 10**9+7
INF = float('inf')

#############
# Functions #
#############

######INPUT######
def inputI(): return int(input().strip())
def inputS(): return input().strip()
def inputIL(): return list(map(int,input().split()))
def inputSL(): return list(map(str,input().split()))
def inputILs(n): return list(int(input()) for _ in range(n))
def inputSLs(n): return list(input().strip() for _ in range(n))
def inputILL(n): return [list(map(int, input().split())) for _ in range(n)]
def inputSLL(n): return [list(map(str, input().split())) for _ in range(n)]

#####Inverse#####
def inv(n): return pow(n, MOD-2, MOD)

######Combination######
kaijo_memo = []
def kaijo(n):
  if(len(kaijo_memo) > n):
    return kaijo_memo[n]
  if(len(kaijo_memo) == 0):
    kaijo_memo.append(1)
  while(len(kaijo_memo) <= n):
    kaijo_memo.append(kaijo_memo[-1] * len(kaijo_memo) % MOD)
  return kaijo_memo[n]

gyaku_kaijo_memo = []
def gyaku_kaijo(n):
  if(len(gyaku_kaijo_memo) > n):
    return gyaku_kaijo_memo[n]
  if(len(gyaku_kaijo_memo) == 0):
    gyaku_kaijo_memo.append(1)
  while(len(gyaku_kaijo_memo) <= n):
    gyaku_kaijo_memo.append(gyaku_kaijo_memo[-1] * pow(len(gyaku_kaijo_memo),MOD-2,MOD) % MOD)
  return gyaku_kaijo_memo[n]

def nCr(n,r):
  if(n == r):
    return 1
  if(n < r or r < 0):
    return 0
  ret = 1
  ret = ret * kaijo(n) % MOD
  ret = ret * gyaku_kaijo(r) % MOD
  ret = ret * gyaku_kaijo(n-r) % MOD
  return ret

######Factorization######
def factorization(n):
    arr = []
    temp = n
    for i in range(2, int(-(-n**0.5//1))+1):
        if temp%i==0:
            cnt=0
            while temp%i==0:
                cnt+=1
                temp //= i
            arr.append([i, cnt])
    if temp!=1:
        arr.append([temp, 1])

    if arr==[]:
        arr.append([n, 1])
    return arr

#####LCM#####
def lcm(a, b):
    return a * b // gcd (a, b)

#############
# Main Code #
#############

N = inputI()
S = list(inputS())
Q = inputI()
Qs = inputSLL(Q)

alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for t,a,b in Qs:
  a = int(a)
  if int(t) == 1:
    bag[S[a-1]].remove(a)
    S[a-1] = b
    bag[b].append(a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      bag[l].sort()
      left = bisect.bisect_left(bag[l],a)
      right = bisect.bisect_right(bag[l],b)
      if left !=  right:
        count += 1
    print(count)

Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import math
from functools import lru_cache

#############
# Constants #
#############

MOD = 10**9 +7
INF = float('inf')

#############
# Functions #
#############

kaijo_memo = []
def kaijo(n):
  if(len(kaijo_memo) > n):
    return kaijo_memo[n]
  if(len(kaijo_memo) == 0):
    kaijo_memo.append(1)
  while(len(kaijo_memo) <= n):
    kaijo_memo.append(kaijo_memo[-1] * len(kaijo_memo) % MOD)
  return kaijo_memo[n]

gyaku_kaijo_memo = []
def gyaku_kaijo(n):
  if(len(gyaku_kaijo_memo) > n):
    return gyaku_kaijo_memo[n]
  if(len(gyaku_kaijo_memo) == 0):
    gyaku_kaijo_memo.append(1)
  while(len(gyaku_kaijo_memo) <= n):
    gyaku_kaijo_memo.append(gyaku_kaijo_memo[-1] * pow(len(gyaku_kaijo_memo),MOD-2,MOD) % MOD)
  return gyaku_kaijo_memo[n]

def nCr(n,r):
  if(n == r):
    return 1
  if(n < r or r < 0):
    return 0
  ret = 1
  ret = ret * kaijo(n) % MOD
  ret = ret * gyaku_kaijo(r) % MOD
  ret = ret * gyaku_kaijo(n-r) % MOD
  return ret

def factorization(n):
    arr = []
    temp = n
    for i in range(2, int(-(-n**0.5//1))+1):
        if temp%i==0:
            cnt=0
            while temp%i==0:
                cnt+=1
                temp //= i
            arr.append([i, cnt])
    if temp!=1:
        arr.append([temp, 1])

    if arr==[]:
        arr.append([n, 1])
    return arr

#############
# Main Code #
#############

N = int(input())
S = list(str(input()))
Q = int(input())

for i in range(Q):
  query = list(map(str,input().split()))
  if query[0] == "1":
    S[int(query[1])-1] = query[2]
  if query[0] == "2":
    print(len(set(S[int(query[1])-1:int(query[2])])))

Fixed submission:
# -*- coding: utf-8 -*-

#############
# Libraries #
#############

import sys
input = sys.stdin.readline

N = int(input())
S = list(input())
Q = int(input())


alphabet = "abcdefghijklmnopqrstuvwxyz"

bag = { l:[] for l in alphabet}

for i in range(N):
  bag[S[i]].append(i+1)


import bisect

for _ in range(Q):
  t,a,b = input().split()
  a = int(a)
  if int(t) == 1:
    if S[a-1]!=b:
      bag[S[a-1]].remove(a)
      S[a-1] = b
      bisect.insort(bag[b],a)
  else:
    count = 0
    b = int(b)
    for l in alphabet:
      if len(bag[l])>0:
        left = bisect.bisect_left(bag[l],a)
        if left != len(bag[l]):
          if bag[l][left] <= b:
            count += 1
    print(count)