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)

n = gets.to_i
$s = gets.chomp

$h = Hash.new{|x,y| x[y] = []}
$s.each_char.with_index {|x, j| $h[x] << j + 1}
$s = " " + $s

def update(b, c)
    return if $s[b] == c
    t, $s[b] = $s[b], c
    $h[t].delete_at($h[t].bsearch_index{|e| e >= b})
    $h[c].insert(($h[c].bsearch_index{|e| e >= b} or -1), b)
end

gets.to_i.times do
    a, b, c = gets.chomp.split
    b = b.to_i

    if a.to_i == 1
        update(b, c)
    else
        c = c.to_i
        p $h.each_value.count{|e| (e.bsearch{|ee| ee >= b} or n) <= c}
    end
end