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: Runtime Error)

from bisect import insort_left, bisect_left, bisect_right

characters = [chr(ord('a') + i) for i in range(26)]

def main():
    N = int(input())
    S = input()
    Q = int(input())

    indices_dict = {a: [] for a in characters}
    for i, s in enumerate(S):
        indices_dict[s].append(i + 1)

    for i in range(Q):
        a, b, c = input().split()
        if int(a) == 2:
            l, r = int(b), int(c)
            cnt = 0
            for c in characters:
                if len(indices_dict[c]) > 0 and \
                    l <= indices_dict[c][-1] and \
                    indices_dict[c][bisect_left(indices_dict[c], l)] <= r:
                    cnt += 1
            print(cnt)
        else:
            from_c = S[ind - 1]
            ind, to_c = int(b), c
            if from_c == to_c:
                continue
            insort_left(indices_dict[to_c], ind)
            indices_dict[from_c].pop(bisect_left(indices_dict[from_c], ind))
            S[ind] = to_c

if __name__ == "__main__":
    main()