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: Runtime Error)

N = gets.to_i
S = gets.chomp
Q = gets.to_i
Query = []

Q.times do
    Query << gets.chomp.split(" ")

s = Hash.new{|h, k| h[k] = []}
(0...N).each do |i|
    s[S[i]] << (i + 1)
end

ans = Array.new(26)

Query.each do |f, a, b|
    if f == "1"
        a = a.to_i
        if S[a - 1] != b
            idx = s[S[a - 1]].bsearch_index{|x| x >= a}
            s[S[a - 1]].delete_at(idx)
            S[a - 1] = b
            idx = s[b.bsearch_index{|x| x >= a}
            idx.nil? ? s[b << a : s[b].insert(idx, a)
        end
    else
        [a, b].map!(&:to_i)
        (0..25).each do |i|
            i_1 = s[(97 + i).chr].bsearch_index{|x| x >= a}
            i_2 = s[(97 + i).chr].bsearch_index{|x| x > b}
            if i_1.nil? 
                ans[i] = 0
            elsif i_2.nil? 
                ans[i] = s[(97 + i).chr].size - i_1
            else
                ans[i] = i_2 - i_1
            end
        end
        puts ans.count{|i| i > 0}
    end
end