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

public class Hello
{
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        var s = Console.ReadLine().Trim();
        var sc = s.ToCharArray();
        var ss = new SortedSet<int>[26];
        for (int i = 0; i < 26; i++) ss[i] = new SortedSet<int>();
        for (int i = 0; i < n; i++) ss[s[i] - 'a'].Add(i);
        var q = int.Parse(Console.ReadLine().Trim());
        for (int i = 0; i < q; i++)
        {
            string[] line = Console.ReadLine().Trim().Split(' ');
            if (line[0] == "1")
            {
                var si = int.Parse(line[1]) - 1;
                var pre = sc[si] - 'a';
                ss[pre].Remove(si);
                var st = line[2][0];
                sc[si] = st;
                ss[st - 'a'].Add(si);
            }
            else
            {
                var count = 0;
                for (int j = 0; j < 26; j++)
                {
                    var L = int.Parse(line[1]) - 1;
                    var r = int.Parse(line[2]) - 1;
                    if (check(ss[j], L, r)) count++;
                }
                Console.WriteLine(count);
            }
        }
    }
    static bool check(SortedSet<int> ss, int L, int r)
    {
        var c = ss.Count();
        var a = new int[c];
        ss.CopyTo(a);
        return LowerBound(a, L) < UpperBound(a, r);
    }
    public static int LowerBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
    {
        int low = start;
        int high = end;
        int mid;
        while (low < high)
        {
            mid = ((high - low) >> 1) + low;
            if (comparer.Compare(arr[mid], value) < 0)
                low = mid + 1;
            else
                high = mid;
        }
        return low;
    }
    public static int LowerBound<T>(T[] arr, T value) where T : IComparable
    {
        return LowerBound(arr, 0, arr.Length, value, Comparer<T>.Default);
    }
    public static int UpperBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
    {
        int low = start;
        int high = end;
        int mid;
        while (low < high)
        {
            mid = ((high - low) >> 1) + low;
            if (comparer.Compare(arr[mid], value) <= 0)
                low = mid + 1;
            else
                high = mid;
        }
        return low;
    }
    public static int UpperBound<T>(T[] arr, T value)
    {
        return UpperBound(arr, 0, arr.Length, value, Comparer<T>.Default);
    }
}