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

a_ord = "a".ord
z = 1 << (n-1).bit_length

st = Array.new(2*z, 0)
s.each_char.with_index(z) {|c,i| st[i] = 1 << c.ord - a_ord}
(z-1).downto(1) {|i| st[i] = st[2*i] | st[2*i+1]}

def calc(st, i, j, k, s, t)
    if s <= j && k <= t
        st[i]
    elsif k < s || t < j
        0
    else
        calc(st, 2*i, j, (j+k)/2, s, t) | calc(st, 2*i+1, (j+k)/2+1, k, s, t)
    end
end

gets
readlines.each do |abc|
    a, b, c = abc.split
    b = b.to_i

    if a == "1"
        c = 1 << c.ord - a_ord
        x = z+b-1
        next if st[x] == c

        st[x] = c
        x /= 2
        while x != 0
            st[x] = st[2*x] | st[2*x+1]
            x /= 2
        end
    else
        x = calc(st, 1, 1, z, b, c.to_i)
        y = 0
        while x != 0
            y += 1
            x &= x - 1
        end
        puts y
    end
end