output_description: For each query of type 2, print a line containing the answer.
  
  * * *
input_description: 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
attempt: from collections import Counter
  
  
  def main():
      n = int(input().strip())
      s = list(input().strip())
  
      bit = [Counter() for _ in range(n + 1)]
  
      def query(i):
          result = Counter()
          while i:
              result += bit[i]
              i -= i & -i
          return result
  
      def update(i, cnt):
          while i < len(bit):
              bit[i] += cnt
              i += i & -i
  
      for i, c in enumerate(s, 1):
          update(i, {c: 1})
  
      q = int(input().strip())
      for _ in range(q):
          Q = input().strip().split()
          if Q[0] == "1":
              i, c = int(Q[1]), Q[2]
              update(i, {s[i - 1]: -1, c: 1})
              s[i - 1] = c
          else:
              cnt = query(int(Q[2])) - query(int(Q[1]) - 1)
              print(len(cnt))
  
  
  main()
  
problem_description: 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).
samples: [{"input": "7\n    abcdbbd\n    6\n    2 3 6\n    1 5 z\n    2 1 1\n    1 4 a\n    1 7 d\n    2 1 7", "output": "3\n    1\n    5\n    \n\nIn the first query, `cdbb` contains three kinds of letters: `b` , `c` , and\n`d`, so we print 3.\n\nIn the second query, S is modified to `abcdzbd`.\n\nIn the third query, `a` contains one kind of letter: `a`, so we print 1.\n\nIn the fourth query, S is modified to `abcazbd`.\n\nIn the fifth query, S does not change and is still `abcazbd`.\n\nIn the sixth query, `abcazbd` contains five kinds of letters: `a`, `b`, `c`,\n`d`, and `z`, so we print 5."}]