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.chomp.to_i
S = gets.chomp
Q = gets.chomp.to_i
a_ord = "a".ord
u = Array.new(Q){Array.new(3)}
for i in 0...Q do
    str = gets.split
    if str[0] == "1"
        str[2] = str[2].ord - a_ord
    end
    u[i][0], u[i][1], u[i][2] = str[0].to_i, str[1].to_i, str[2].to_i
end
t = Array.new(S.size)
a = Array.new(26){Array.new(1,0)}
for i in 0...S.size do
    x = S[i].ord - a_ord
    t[i] = x
    a[x].push(i+1)
end
for i in 0...26 do
    a[i].push(N+1)
end

for i in 0...Q do
    if u[i][0] == 1
        x = u[i][1]
        y = u[i][2]
        z = t[x-1]
        l = 0
        r = a[z].size-1
        while l != r
            c = (l+r)/2
            if a[z][c] == x
                l = c
                r = c
            elsif a[z][c] < x
                l = c+1
            else
                r = c-1
            end
        end
        a[z].delete_at(l)
        t[x-1] = y
        l = 0
        r = a[y].size-1
        while r-l > 2
            c = (l+r)/2
            if a[y][c] < x
                l = c
            else
                r = c
            end
        end
        a[y].insert(r,x)
    else
        answer = 0
        d = u[i][1]
        e = u[i][2]
        for j in 0...26 do
            l = 0
            r = a[j].size-1
            while r-l > 1
                c = (l+r)/2
                if a[j][c] == d
                    l = c-1
                    r = c
                elsif a[j][c] < d
                    l = c
                else
                    r = c
                end
            end
            r1 = r
            l = 0
            r = a[j].size-1
            while r-l > 1
                c = (l+r)/2
                if a[j][c] == e
                    l = c
                    r = c+1
                elsif a[j][c] < e
                    l = c
                else
                    r = c
                end
            end
            l2 = l
            if r1 <= l2
                answer += 1
            end
        end
        puts answer
    end
end