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 Java8 (OpenJDK 1.8.0) (judge verdict: Time Limit Exceeded)

import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        int n = scanner.nextInt();
        String s = scanner.next();
        int q = scanner.nextInt();
        char[] chars = s.toCharArray();

        for( int i = 0 ; i < q ; i++){
            int type = scanner.nextInt();
            int q1 = scanner.nextInt();
            String q2 = scanner.next();

            if(type == 1){
                chars[q1 - 1] = q2.toCharArray()[0];

            }else if(type == 2){
                Set<Character> cs = new HashSet<>();
                int max = Integer.parseInt(q2);
                for(int j = q1 ; j <= max ; j++){
                    cs.add(chars[j - 1]);
                }
                System.out.println(cs.size());
            }
        }
        System.exit(0);
    }
}