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 (7.3.0) (judge verdict: Wrong Answer)

N=int(input())
S=input()
slst=[s for s in S]
Q=int(input())

class Bit:
    def __init__(self, n):
        self.size = n
        self.tree = [0] * (n + 1)
 
    def sum(self, i):
        s = 0
        while i > 0:
            s += self.tree[i]
            i -= i & -i
        return s
 
    def add(self, i, x):
        while i <= self.size:
            self.tree[i] += x
            i += i & -i
 
bits=[Bit(N) for _ in range(26)]

for i in range(N):
    ch=ord(S[i])-ord('a')
    bits[ch].add(i+1,1)

for _ in range(Q):
    t,a,b=input().split()

    if t=='1':
        a=int(a)
        pos=a-1
        nextc=ord(b)-ord('a')
        beforec=ord(slst[pos])-ord('a')

        if nextc!=beforec:
            bits[beforec].add(a,-1)
            bits[nextc].add(a,1)
    else:
        l=int(a)
        r=int(b)

        cnt=[0]*26

        for i in range(26):
            cnt[i]+=bits[i].sum(r)
        
        if l-1>0:
            for i in range(26):
                cnt[i]-=bits[i].sum(l-1)
        
        ans=0

        for i in range(26):
            if cnt[i]>0:
                ans+=1
        
        print(ans)