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: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
using static System.Console;
using System.Text;
using System.IO;
using static System.Math;
namespace AtCoder
{
    class Program
    {
        static public long[] Sarray() { return ReadLine().Split().Select(long.Parse).ToArray(); }
        static public List<long> Slist() { return ReadLine().Split().Select(long.Parse).ToList(); }
        static void Main(string[] args)
        {
            SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
            Solve();
            Out.Flush();
            Read();
        }
        static void Solve()
        {
            var N = Sarray()[0];
            var segs = Enumerable.Range(0, 'z' - 'a' + 1).Select(_ => new SegmentTree<bool>((int)N, (b1, b2) => b1 | b2, false)).ToArray();
            var S = ReadLine().ToCharArray();
            for (var i = 0; i < N; ++i)
                segs[S[i] - 'a'].update(i, true);
            var Q = Sarray()[0];
            for (var i = 0; i < Q; ++i)
            {
                var query = ReadLine().Split();
                var t = int.Parse(query[0]);
                if (t == 1)
                {
                    var iq = int.Parse(query[1]) - 1;
                    segs[S[iq] - 'a'].update(iq, false);
                    S[iq] = query[2][0];
                    segs[S[iq] - 'a'].update(iq, true);
                }
                if (t == 2)
                {
                    var lq = int.Parse(query[1]) - 1;
                    var rq = int.Parse(query[2]);
                    var ans = 0;
                    for (var j = 0; j < 26; ++j)
                        if (segs[j].query(lq, rq)) ++ans;
                    WriteLine(ans);
                }
            }
        }
        class SegmentTree<Monoid>
        {
            int sz;
            Monoid[] seg;
            readonly Func<Monoid, Monoid, Monoid> f;
            readonly Monoid M1;
            //数、操作、初期値
            public SegmentTree(int n, Func<Monoid, Monoid, Monoid> f, Monoid M1)
            {
                this.f = f;
                this.M1 = M1;
                sz = 1;
                while (sz < n) sz <<= 1;
                seg = new int[sz * 2].Select(_ => M1).ToArray();
            }
            public void set(int k, Monoid x) => seg[k + sz] = x;
            public void build()
            {
                for (int k = sz - 1; 0 < k; --k)
                    seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
            }
            public void update(int k, Monoid x)
            {
                k += sz;
                seg[k] = x;
                while (0 != (k >>= 1))
                    seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
            }
            //区間[a,b)に対して
            public Monoid query(int a, int b)
            {
                Monoid L = M1, R = M1;
                for (a += sz, b += sz; a < b; a >>= 1, b >>= 1)
                {
                    if (0 != (a & 1)) L = f(L, seg[a++]);
                    if (0 != (b & 1)) R = f(seg[--b], R);
                }
                return f(L, R);
            }
            public Monoid this[int k] => seg[k + sz];
        }
    }
}