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.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;
 
public class Main {
 
	public static final MyScanner in = new MyScanner();
 
	public static void main(String[] args) {
 
		int N  = in.nextInt();
		char[] S = in.next().toCharArray();
		int Q = in.nextInt();

		List<Integer> answer = new ArrayList<>();
		for(int i=0;i<Q;i++) {
			int type = in.nextInt();
			if (type == 1) {
				int pos = in.nextInt();
				char target = in.next().charAt(0);
				S[pos-1] = target;
			} else {
				int l = in.nextInt();
				int r = in.nextInt();
				Set<Character> s = new HashSet<>();
				for (int j=l-1;j<r;j++) {
					s.add(S[j]);
				}
				answer.add(s.size());
			}
		}
		answer.forEach(System.out::println);
	}

	public static class MyScanner{
		Scanner sc = new Scanner(System.in);
		String nextLine() {return sc.nextLine();}
		String next() {return sc.next();}
		int nextInt() {return Integer.valueOf(sc.next());}
		long nextLong() { return Long.valueOf(sc.next());}
	}

}