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;
using System.Threading.Tasks;

namespace AtCoder.Abc
{
    class CharEqualityComparer : IEqualityComparer<char>
    {
        public bool Equals(char b1, char b2)
        {
            return b1 == b2;
        }

        public int GetHashCode(char bx)
        {
            return bx.GetHashCode();
        }
    }

    class QuestionD
    {
        public static void Main(string[] args)
        {
            var com = new CharEqualityComparer();
            var abc = "abcdefghijklmnopqrstuvwxyz";

            var sw = new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);

            // 整数の入力
            var n = int.Parse(Console.ReadLine());

            // 文字列の入力
            string s = Console.ReadLine();

            // 整数の入力
            var q = int.Parse(Console.ReadLine());

            for(int i = 0; i < q; i++) {
                var inputStrArray = Console.ReadLine().Split(' ');

                if(inputStrArray[0] == "1") {
                    var index = int.Parse(inputStrArray[1]) - 1;

                    if(s[index] != inputStrArray[2][0]) {
                        s = s.Substring(0, index) + inputStrArray[2] + s.Substring(index + 1);
                    }
                } else {
                    var index1 = int.Parse(inputStrArray[1]) - 1;
                    var index2 = int.Parse(inputStrArray[2]) - 1;
                    var newS = s.Substring(index1, index2 - index1 + 1);
                    var count = 0;
                    foreach(var c in abc) {
                        if (newS.Contains(c, com)) {
                            count++;
                        }
                    }

                    Console.WriteLine(count);
                }
            }

            Console.Out.Flush();
        }
    }
}