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)

def get_i() #空白区切の入力を数値(整数)の配列で返す
  return gets.chomp.split(" ").map(&:to_i)
end
def get_f() #空白区切の入力を数値(実数)の配列で返す
  return gets.chomp.split(" ").map(&:to_f)
end
def get() #空白区切の入力を文字列の配列で返す
  return gets.chomp.split(" ")
end
def get_nsp() #入力されたものを一文字ずつに区切った文字列の配列で返す
  return gets.chomp.split("")
end
def yn_judge(bool,y="Yes",n="No") #boolに真偽を投げることで、trueならy、falseならnの値を出力する
  return bool ? y : n 
end
def array(size,n=1,init=nil) #nに配列の次元数、sizeに配列の大きさ、initに初期値を投げることでその配列を返す
  if n==1
    return Array.new(size){init}
  else
    return Array.new(n).map{Array.new(size){init}}
  end
end

class BIT
  attr_accessor:node,:n
  def initialize(n)
    @n=n
    @node=array(@n+1,1,0)
  end

  def update(i,x)
    while i<=@n
      @node[i]+=x
      i+=i&-i
    end
  end

  def sum(i)
    s=0
    while i>0
      s+=@node[i]
      i-=i&-i
    end
    return s
  end
  def getSum(s,t)
    return sum(t)-sum(s)
  end
end
$exchange={}
("a".."z").to_a.each_with_index do|c,i|
  $exchange[c]=i
end
n=gets.to_i
s=get_nsp
q=gets.to_i
bit=array(26,1)
26.times do|i|
  bit[i]=BIT.new(n)
end
n.times do|i|
  bit[$exchange[s[i]]].update(i+1,1)
end
q.times do
  que=get
  if que[0].to_i==1
    next if s[que[1].to_i-1]==que[2]
    bit[$exchange[s[que[1].to_i-1]]].update(que[1].to_i,-1)
    bit[$exchange[que[2]]].update(que[1].to_i,1)
  else
    ans=0
    26.times do|i|
      val=bit[i].getSum(que[1].to_i-1,que[2].to_i)
      ans+=1 if val>0
    end
    puts ans
  end
end