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: Wrong Answer)

import java.util.*;

public class Main {
    public static void main(String args[]) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String s = sc.next();
        int q = sc.nextInt();
        
        Map<Character, TreeSet<Integer>> charRangeMap = new HashMap<>();
        for(int i = 0; i < s.length(); i++) {
           char c = s.charAt(i);
           if(!charRangeMap.containsKey(c))
             charRangeMap.put(c, new TreeSet<>());
           charRangeMap.get(c).add(i);
        }
        char[] charArray = s.toCharArray();
        for(int i = 0; i < q; i++) {
            int oper = sc.nextInt();
            if(oper == 1) {
                int idx = sc.nextInt() - 1;
                char newChar = sc.next().charAt(0);
                char originalChar = charArray[idx];
                if(originalChar == newChar) continue;
                charArray[idx] = newChar;
                if(!charRangeMap.containsKey(newChar)) {
                    charRangeMap.put(newChar, new TreeSet<>());
                }
                charRangeMap.get(originalChar).remove(idx);
                charRangeMap.get(newChar).add(idx);
            } else {
                int left = sc.nextInt() - 1;
                int right = sc.nextInt() - 1;
                int cnt = 0;
                for(Map.Entry<Character, TreeSet<Integer>> entry : charRangeMap.entrySet()) {
                     TreeSet<Integer> range = entry.getValue();
                     if(range.size() == 0 || range.first() > right || range.last() < left) continue;
                     else cnt++;
                }
                System.out.println(cnt);
            }
        }
    }
}