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)

n = int(input())
s = input()
q = int(input())
commands = []
for _ in range(q):
    com, x, y = input().split()
    commands.append((com, int(x), y))

size = 1
while size < n:
    size *= 2

# initialize
segment_tree = [0 for _ in range(2 * size - 1)]


def alphabet2bit(string):
    return 1 << (ord(string) - ord('a'))

def update(i, x, segment_tree):
    i += size - 1
    segment_tree[i] = alphabet2bit(x)
    while i > 0:
        i = (i - 1) // 2
        left = segment_tree[i * 2 + 1]
        right = segment_tree[i * 2 + 2]
        segment_tree[i] = left | right

def getSum(s, t, k, l, r, segment_tree):
    if r <= s or t <= l:
        return 0
    if s <= l and r <= t:
        return segment_tree[k]
    else:
        ask_left = getSum(s, t, k * 2 + 1, l, (l + r) // 2, segment_tree)
        ask_right = getSum(s, t, k * 2 + 2, (l + r) // 2, r, segment_tree)
        return ask_left | ask_right

for i in range(n):
    update(i, s[i], segment_tree)

for com, x, y in commands:
    if com == '1':
        update(x - 1, y, segment_tree)
    else:
        result = getSum(x - 1, int(y), 0, 0, size, segment_tree)
        print(bin(result).count('1'))