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;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            input_iter = LazyLoadAllLines();
            //------------------------------------------------//
            //var n = Read<long>();
            //var s = Read();
            //var als = Read<long>(n);
            //var sls = Read(n);
            /*List<Tuple<string, long>> scls = new List<Tuple<string, long>>();
            for (int i = 0; i < m; ++i)
            {
                scls.Add(Tuple.Create(Read(), Read<long>()));
            }*/
            //List<List<long>> abls = new List<List<long>>();
            //List<long> cls = new List<long>();
            /*List<long> edgeNum = Enumerable.Repeat(0L, (int)n).ToList();
            for (int i = 0; i < n - 1; ++i)
            {
                abls.Add(Read<long>(2));
                abls[i].Add(i);
                abls[i].Add(-1);
                --abls[i][0];
                --abls[i][1];
                //cls.Add(Read<long>());
                ++edgeNum[(int)abls[i][0]];
                ++edgeNum[(int)abls[i][1]];
            }*/

            //als.Sort((l, r) => (r - l));
            //sls.Sort(StringComparer.OrdinalIgnoreCase);

            var n = Read<int>();
            var s = Read().ToCharArray();
            var q = Read<long>();
            for (int i = 0; i < q; ++i)
            {
                var first = Read<int>();
                if(first == 1)
                {
                    var idx = Read<int>();
                    var c = Read<char>();

                    s[idx - 1] = c;
                }
                else
                {
                    int left = Read<int>();
                    int right = Read<int>();
                    //bool[] checker = new bool[26];

                    Console.WriteLine(new string(s).Substring(left - 1, right - left + 1).Distinct().Count());
                    /*for (int j = left - 1; j < right; ++j)
                    {
                        checker[s[j] - 'a'] = true;
                    }*/

                }
            }

            /*var n = Read<int>();
            var m = Read<long>();
            var k = Read<long>();*/

            /*Dictionary<int, List<int>> abdic = new Dictionary<int, List<int>>();
            for (int i = 1; i <= n; ++i) abdic[i] = new List<int>();

            for (int i = 0; i < m; ++i)
            {
                var val = Tuple.Create(Read<int>(), Read<int>());
                if (val.Item1 > val.Item2) val = Tuple.Create(val.Item2, val.Item1);
                abdic[val.Item1].Add(val.Item2);
            }

            /*List<Tuple<int, int>> abls = new List<Tuple<int, int>>();
            for (int i = 0; i < m; ++i)
            {
                var val = Tuple.Create(Read<int>(), Read<int>());
                if (val.Item1 > val.Item2) val = Tuple.Create(val.Item2, val.Item1);
                abls.Add(val);
            }
            abls.Sort();*/
            /*int[][] abmx = new int[n + 1][];
            for (int i = 0; i < m; ++i)
            {
                abmx[i + 1] = new int[n + 1];
            }
            for (int i = 0; i < m; ++i)
            {
                abmx[i + 1] = new int[n + 1];
                var val = Tuple.Create(Read<int>(), Read<int>());
                abmx[val.Item1][val.Item2] = 1;
                abmx[val.Item2][val.Item1] = 1;
            }*/

            /*List<Tuple<int, int>> cdls = new List<Tuple<int, int>>();
            for (int i = 0; i < m; ++i)
            {
                var val = Tuple.Create(Read<int>(), Read<int>());
                if (val.Item1 > val.Item2) val = Tuple.Create(val.Item2, val.Item1);
                cdls.Add(val);
            }
            cdls.Sort();

            bool[] checklist = new bool[n + 1];
            checklist[1] = true;
            int curId = 1;
            HashSet<int> friends = new HashSet<int>();

            Queue<int> queue = new Queue<int>();
            while(checklist.All(v => v))
            {
                friends.Add(curId);
                var friSize = friends.Count();

                while(friSize == friends.Count())
                {
                    foreach (var x in abdic[curId])
                    {
                        queue.Enqueue(x);
                        friends.Add(x);
                    }
                }
            }*/

            // 1 2 3 4
            // 1 2
            // 1 3
            // 2 3
            // 3 4

            // 1 4

            //Console.WriteLine(-1);
        }

        static IEnumerator<string> input_iter;

        static IEnumerator<string> LazyLoadAllLines(bool doSplit = true)
        {
            string line;
            if (doSplit)
            {
                do
                {
                    line = Console.ReadLine();
                    foreach (var s in line.Split(' '))
                        yield return s;
                } while (line != null);
            }
            else
            {
                do
                {
                    line = Console.ReadLine();
                    yield return line;
                } while (line != null);
            }
        }
        static _T Read<_T>() where _T : struct
        {
            input_iter.MoveNext();
            return (_T)Convert.ChangeType(input_iter.Current, typeof(_T));
        }
        static string Read()
        {
            input_iter.MoveNext();
            return input_iter.Current;
        }
        static List<_T> Read<_T>(long num) where _T : struct
        {
            List<_T> res = new List<_T>();
            for (long i = 0; i < num; ++i)
            {
                input_iter.MoveNext();
                res.Add((_T)Convert.ChangeType(input_iter.Current, typeof(_T)));
            }
            return res;
        }
        static List<string> Read(long num)
        {
            List<string> res = new List<string>();
            for (long i = 0; i < num; ++i)
            {
                input_iter.MoveNext();
                res.Add(input_iter.Current);
            }
            return res;
        }

    }
}