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

class Program
{
    static void Main(string[] args) {
#if DEBUG
        MyDebugger.Test(process, "../TextFile1.txt");
        //MyDebugger.Test(process, "../TextFile2.txt");
        //MyDebugger.MakeTestCase("../TextFile2.txt");
#else
        object ret = process(new StreamReader(Console.OpenStandardInput()));
        Console.WriteLine(ret);
#endif
    }

    //static long mod = 1000000007;
    static HashSet<int>[] friends;
    static HashSet<int>[] blocks;
    static HashSet<int>[] friends2;

    static object process(TextReader input) {
        var n = int.Parse(input.ReadLine());
        var s = input.ReadLine();
        var q = int.Parse(input.ReadLine());

        StringBuilder str = new StringBuilder(s);

        for(int i=0; i<q; i++) {
            var spl   = input.ReadLine().Split(' ');
            var a     = int.Parse(spl[0]);

            if(a == 1) {
                var b = int.Parse(spl[1]);
                var c = spl[2][0];

                str[b - 1] = c;
            } else {
                var b = int.Parse(spl[1]);
                var c = int.Parse(spl[2]);

                Console.WriteLine(Count(str, b - 1, c - 1).ToString());
            }
        }

        return null;
    }

    private static int Count(StringBuilder s, int x1, int x2) {
        var hash = new HashSet<char>();

        for(int i=x1; i<=x2; i++) {
            char c = s[i];
            if (!hash.Contains(c)) hash.Add(c);
        }

        return hash.Count;
    }
}