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 Python (3.4.3) (judge verdict: Time Limit Exceeded)

N = int(input())
S = input()
Q = int(input())
Query = []
for i in range(Q):
  Query.append(list(map(str, input().split())))

for i in range(Q):
  if Query[i][0] == '1':
    if Query[i][1]=='1':
      S = Query[i][2] + S[1:]
    elif int(Query[i][1]) == N:
      S = S[:N-1] + Query[i][2]
    else:
      S = S[:int(Query[i][1])-1] + Query[i][2] + S[int(Query[i][1]):]
  elif Query[i][0] == '2':
    ii = int(Query[i][1])
    jj = int(Query[i][2])
    SS = S[ii-1:jj]
    ss = []
    for m in range(len(SS)):
      add = False
      for n in range(len(ss)):
        if ss[n] == SS[m]:
          add = True
          break
      if not add:
        ss.append(SS[m])
    print(len(ss))