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: Runtime Error)

import bisect
import sys
sys.setrecursionlimit(10**9)

def main():
    N = int(input())
    S = list(input())

    a_ord = ord('a')
    z_ord = ord('z')

    set_list = [set() for _ in range(z_ord+1)]
    for i in range(N):
        s = S[i]
        set_list[ord(s)].add(i)

    Q = int(input())
    for q in range(Q):
        ipt = input().split()
        if ipt[0] == "1":
            i,c = int(ipt[1]), ipt[2]
            s = S[i-1]

            set_list[ord(s)].remove(i-1)
            set_list[ord(c)].add(i-1)

        else:
            l,r = int(ipt[1]), int(ipt[2])
            ans = 0
            # if l == r:
            #     print(1)
            #     continue

            for i in range(a_ord,z_ord+1):
                st = list(set_list[i])
                if not len(st) > 0: continue

                # print(i,set_list[i])
                l_p = bisect.bisect_left(st,l-1)
                r_p = bisect.bisect_right(st,r-1)

                # print(l-1,r-1,l_p,r_p)
                if l_p < r_p:
                    ans += 1

            # print(ans,"____")
            print(ans)



if __name__ == "__main__":
  main()