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: Time Limit Exceeded)

#https://atcoder.jp/contests/abc157/submissions/10472866

#https://docs.ruby-lang.org/ja/latest/class/SortedSet.html
#https://msp-greg.github.io/ruby_2_2/set/Set.html#union-instance_method

require 'set'

class SortedSet
  def lower_bound(x)
    self.to_a.bsearch{|n| n >= x }
  end
end

N = gets.to_i
s = gets.chomp
Qnum = gets.to_i
Q = Qnum.times.map{gets.split}

=begin
N = 500000
s = N.times.map{ (97 + rand(26)).chr }.join
Qnum = 20000
q = (3).times.map{[1, rand(1..N), (97 + rand(26)).chr ]}
q += (Qnum - 3).times.map{[2, 1, rand(1..10)]}
Q = q.shuffle
=end

tree = Array.new(26){ SortedSet.new }

N.times do |i|
  tree[s[i].ord - 97].add(i)
end


Q.each do |type, x, y|
  if type.to_i == 1
    i = x.to_i-1
    next if y == s[i]
    tree[s[i].ord - 97].delete(i)
    s[i] = y
    tree[s[i].ord - 97].add(i)
  else
    l, r = x.to_i-1, y.to_i-1
    ans = 0
    26.times do |i|
      num = tree[i].lower_bound(l)
      if num
        ans += 1 if num <= r
      end
    end
    puts ans
  end
end