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;
class Program
{
    static void Main(string[] args)
    {
            // 入力
            string s2 = System.Console.ReadLine().Trim();
            int iN = int.Parse(s2);
            string sB = System.Console.ReadLine().Trim();
            List<char> sS = sB.ToList();
            s2 = System.Console.ReadLine().Trim();
            int iQ = int.Parse(s2);
            List<ClsQue> lstQue = new List<ClsQue>();
            for (int i = 0; i < iQ; i++)
            {
                string[] sQ = System.Console.ReadLine().Trim().Split(' ');
                ClsQue oneUsr = new ClsQue();
                oneUsr.iT = int.Parse(sQ[0]);
                switch (oneUsr.iT)
                {
                    case 1:
                        oneUsr.iI = int.Parse(sQ[1]) - 1;
                        oneUsr.cC = sQ[2][0];
                        break;
                    case 2:
                        oneUsr.iL = int.Parse(sQ[1]) - 1;
                        oneUsr.iR = int.Parse(sQ[2]) - 1;
                        break;
                }
                lstQue.Add(oneUsr);
            }

            System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
            sw.Start();

            // 解析
            List<int> iOut = new List<int>();
            for (int i = 0; i < lstQue.Count; i++)
            {
                switch (lstQue[i].iT)
                {
                    case 1:
                        sS[lstQue[i].iI] = lstQue[i].cC;
                        break;
                    case 2:
                        List<char> cBuf = new List<char>();
                        for (int j = lstQue[i].iL; j <= lstQue[i].iR; j++)
                        {
                            cBuf.Add(sS[j]);
                        }
                        iOut.Add(cBuf.Distinct().ToList().Count);
                        break;
                }
            }

            // 出力
            for (int i = 0; i < iOut.Count; i++)
            {
                System.Console.WriteLine("{0}", iOut[i].ToString().Trim());
            }

            sw.Stop();
#if DEBUG
            Console.WriteLine();
            Console.WriteLine("{0}", sw.Elapsed.ToString());
            Console.WriteLine("続行するには何かキーを押してください．．．");
            Console.ReadKey();
#endif
    }

        // Query情報
        private class ClsQue
        {
            public int  iT { get; set; } = 0;               // Type
            public int  iI { get; set; } = 0;               // 文字目     0始まり
            public char cC { get; set; } = ' ';             // 変換Char
            public int  iL { get; set; } = 0;               // 開始文字目 0始まり
            public int  iR { get; set; } = 0;               // 終了文字目 0始まり
        }

}