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)

def main():
    n = int(input().strip())
    s = list(input().strip())

    bit = [[0] * 26 for _ in range(n + 1)]

    def query(i):
        result = [0] * 26
        while i:
            for j, x in enumerate(bit[i]):
                result[j] += x
            i -= i & -i
        return result
    
    def update(i, c, val):
        j = ord(c) - ord("a")
        while i < len(bit):
            bit[i][j] += val
            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)
            update(i, c, 1)
            s[i - 1] = c
        else:
            l, r = int(Q[1]), int(Q[2])
            cnt = [x - y for x, y in zip(query(r), query(l - 1))]
            print(sum(x > 0 for x in cnt))


main()