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 PyPy3 (2.4.0) (judge verdict: Accepted)

N = int(input())
S = [ord(i) - 97 for i in input()]
Q = int(input())

# 添字が1から始まることに注意
class BinaryIndexedTree() :
  def __init__(self, N) :
    self.size = N
    self.tree = [0] * (N + 1)
      
  def sum(self, i) :
    s = 0
    while i > 0 :
      s += self.tree[i]
      i -= i & -i
    return s
      
  def add(self, i, x) :
    while i <= self.size :
      self.tree[i] += x
      i += i & -i
      
alph = [BinaryIndexedTree(N + 10) for _ in range(26)]
for i in range(N) :
  alph[S[i]].add(i + 1, 1)

for _ in range(Q) :
  type, x, y = input().split()
  if type == '1' :
    x = int(x)
    s = S[x - 1]
    alph[s].add(x, -1)
    alph[ord(y) - 97].add(x, 1)
    S[x - 1] = ord(y) - 97
  else :
    x, y = int(x), int(y)
    ret = 0
    for i in range(26) :
      if alph[i].sum(y) - alph[i].sum(x - 1) > 0 :
        ret += 1
    print(ret)