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
Q=gets.to_i
qs=$<.read.split.each_slice(3)

size = 1
size *= 2 while size < N

@tree=Array.new(size*2+1) { Hash.new(0) }
def update_(x,c,i)
  if @tree[i][x]
    @tree[i][x] -= 1
    @tree[i].delete(x) if @tree[i][x] <= 0
  end
  @tree[i][c] += 1
  return if i == 0
  update_(x,c,(i-1)/2)
end

def update(c,size,i)
  return if @s[i] == c
  x =@s[i]
  @s[i] = c
  update_(x,c,size+i)
end

def query(a,b,k,l,r)
  return {} if r <= a || b <= l
  return @tree[k] if a <= l && r <= b
  vl = query(a,b,k*2+1,l,(l+r)/2)
  vr = query(a,b,k*2+2,(l+r)/2,r)
  vl.merge(vr)
end

@s.each_char.with_index do |c,i|
  update_('-', c,N+i)
end

qs.each do |a,b,c|
  # p @tree
  # p [a,b,c]
  if a == '1'
    update(c,size, b.to_i-1)
  else
    p query(b.to_i-1,c.to_i,0,0,size).keys.count
  end
end