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 C# (Mono 4.6.2.0) (judge verdict: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ABC157 {
    public class E {
        static void Main(string[] args) {
            Console.ReadLine();
            var chars = Console.ReadLine().ToCharArray();

            var queryCount = Console.ReadLine().Split(' ').Select(int.Parse).Single();
            var queries = new List<string[]>();
            for (int i = 0; i < queryCount; i++) {
                queries.Add(Console.ReadLine().Split(' ').ToArray());
            }
            foreach(var query in queries) { 
                if(query[0] == "1") {
                    // type1
                    var idx = int.Parse(query[1])-1;
                    var newChar = query[2].Single();
                    chars[idx] = newChar;
                } else {
                    // type2
                    var dict = new HashSet<char>();
                    var start = int.Parse(query[1]) - 1;
                    var end = int.Parse(query[2]);
                    var length = end - start;
                    foreach(var c in chars.Skip(start).Take(length)) {
                        if (!dict.Contains(c)) dict.Add(c);
                    }
                    Console.WriteLine(dict.Count);
                }
            }
        }
    }
}