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 (3.8.2) (judge verdict: Accepted)

n = int(input())
s = list(input())
s = [ord(i)-97 for i in s]

dic = {}
for i in range(26):
    dic[i] = []

for i in range(n):
    dic[s[i]].append(i)

for i in range(26):
    dic[i].append(float('inf'))

from bisect import bisect_left
q = int(input())
for i in range(q):
    x, y, z = input().split()
    if x == '1':
        y, z = int(y) - 1, ord(z) - 97
        p = bisect_left(dic[s[y]], y)
        dic[s[y]].pop(p)
        dic[z].insert(bisect_left(dic[z], y), y)
        s[y] = z
    else:
        res = 0
        y, z = int(y) - 1, int(z) - 1
        for i in range(26):
            p = dic[i][bisect_left(dic[i], y)]
            if p <= z:
                res += 1
        print(res)