### BUGGY CODE ###

# -*- 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 CODE ###

# -*- 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)