Problem:
Score : 500 points

Problem Statement

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 1

7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7

Sample Output 1

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.

Solution in Ruby (2.3.3) (judge verdict: Wrong Answer)

#exec({'RUBY_THREAD_VM_STACK_SIZE'=>'100000000'},'/usr/bin/ruby', $0) if !ENV['RUBY_THREAD_VM_STACK_SIZE']
#require 'prime' .prime_division
#ary.bsearch {|x| x >=   4 } ary.bsearch_index { |x| x >=   4 }

@r = 10**9+7

def inpf() a=gets.chomp.split(" ").map(&:to_f)end

def inps() a=gets.chomp.split(" ")end

def copy(a) Marshal.load(Marshal.dump(a)) end

def kaijo(n,r = 10**9+7)(n < 2)? 1 : (2..n).inject{|memo,u|memo=(memo*u)%r} end

def na(n,d=0) Array.new(n,d)end

def na2(n,m,d=0) Array.new(n){Array.new(m,d)}end

def na3(n,m,l,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end

def inp() a=gets.chomp.split(" ").map(&:to_i)end

def r_up(a, b) (a+b-1)/b end

def sum(a) a.inject(:+) end

def big(a,b) return (a>b)? a:b end

def small(a,b) return (a<b)? a:b end


def ins(bit,ind,pl,c)
  while ind < bit.size
    bit[ind][c] += 1
    ind += ind & -ind
  end
end

def pop(bit,c)
  pl = bit.size
  ind = pl -1
  pl >>= 1
  return false if(bit[-1] < c)
  while pl > 0
    if(bit[ind] < c)
      c -= bit[ind]
      ind += pl
    else
      ind -= pl
    end
    pl >>= 1
  end
  return ind  if(bit[ind] == c)
  pl = 1
  if(bit[ind] < c)
    ind += 1
  else
    ind -= 1
  end
  return ind
end

def b_sum (bit, ind)
  sum = na(26)
  while ind > 0
    26.times do |i|
      sum[i] += bit[ind][i]
    end
    ind -= ind & -ind
  end
  return sum
end
n = inp[0]
s = gets.chomp
bit = na2(5*10**5+1,26)
s.each_char.with_index do |c,i|
  ins(bit,i+1,1,c.ord - "a".ord)
end
q = inp[0]
q.times do
  a,b,c = inps
  if(a=="1")
    a,b = a.to_i,b.to_i
    ins(bit,b,-1,s[b-1].ord - "a".ord)
    ins(bit,b,1,c.ord - "a".ord)
    s[b-1] = c
  else
    a,b,c = a.to_i,b.to_i,c.to_i
    d1 = b_sum(bit, c)
    d2 = b_sum(bit, b-1)
    ans = 0
    (26).times do |i|
      ans += 1 if d1[i] - d2[i] > 0
    end
    p ans
  end
end
=begin
7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7
=end