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 (3.4.3) (judge verdict: Time Limit Exceeded)

import numpy as np
n = int(input())
s = input()
q = int(input())
al = "abcdefghijklmnopqrstuvwxyz"


def get(i):
    return np.identity(26)[al.index(i)]


bit = [np.zeros(26) for _ in range(n+1)]


def ko(i, j):
    global bit
    while i <= n:
        bit[i] += j
        i += i & (-i)


def su(i):
    s = np.zeros(26)
    while i != 0:
        s += bit[i]
        i -= i & (-i)
    return s


a = []
for i in range(n):
    ko(i + 1, get(s[i]))
    a.append(get(s[i]))
for _ in range(q):
    kind, i, j = [k for k in input().split()]
    i = int(i)
    if int(kind) == 1:
        ko(i, get(j)-a[i-1])
        a[i-1] = get(j)
    else:
        j = int(j)
        b = su(j) - su(i-1)
        k = 0
        for i in b:
            if i != 0:
                k += 1
        print(k)