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)

#1indexed
class BIT():
    def __init__(self, n):
        self.size = n
        self.bit = [0] * (n+1)

    def sum(self, i):
        s = 0
        while i > 0:
            s += self.bit[i]
            i -= i & -i
        return s

    def add(self, i, x):
        while i <= self.size:
            self.bit[i] += x
            i += i & -i

n = int(input())
s = input()
q = int(input())

bit = [BIT(n+1) for i in range(26)]
for i in range(n):
    bit[ord(s[i])-97].add(i+1, 1)


s = list(s)
for _ in range(q):
    query, a, b = input().split()
    if query == "1":
        i = int(a)
        c = ord(b)-97
        bit[ord(s[i-1])-97].add(i, -1)
        bit[c].add(i, 1)
        s[i-1] = b
    else:
        ans = 0
        for k in range(26):
            if bit[k].sum(int(b))-bit[k].sum(int(a)-1) >= 1:
                ans += 1
        print(ans)