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: Accepted)

N = gets.to_i
S = gets.chomp.chars
Q = gets.to_i.times.map{ gets.split }

A_ORD = 'a'.ord
L = 1 << (N - 1).bit_length
ST = Array.new(2 * L, 0)
S.each_with_index do |c,i|
  ST[L + i] = (1 << (c.ord - A_ORD))
end
(1 ... L).each do |i|
  j = L - i
  ST[j] = (ST[2 * j] | ST[2 * j + 1])
end

class << ST
  def update(i, c)
    self[L + i] = (1 << (c.ord - A_ORD))
    j = (L + i) / 2
    while j > 0
      self[j] = self[2 * j] | self[2 * j + 1]
      j /= 2
    end
  end
  def kind(a, b)
    _query(a, b, 1, 0, L).to_s(2).count('1')
  end
  def _query(a, b, k, l, r)
    return 0 if r <= a || l >= b
    return self[k] if a <= l && r <= b
    mid = (l + r) / 2
    return _query(a, b, 2 * k, l, mid) | _query(a, b, 2 * k + 1, mid, r)
  end
end


Q.each do |q|
  t = q.shift.to_i
  if t == 1
    i = q.shift.to_i - 1
    c = q.shift
    ST.update(i, c)
    S[i] = c
  else
    a = q.shift.to_i - 1
    b = q.shift.to_i - 1
    puts ST.kind(a, b + 1)
  end
end