using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace AtCorder
{
	public class Program
	{
		static void Main(string[] args)
		{
			var cin = new Scanner2();
			int n = cin.Int();
			string s = cin.Next();
			int q = cin.Int();
			char[] ss = s.Select(x => (char)(x - 'a')).ToArray();

			var segs = new LazySegmentTree<int>[26];
			for (int i = 0; i < 26; i++) {
				segs[i] = new LazySegmentTree<int>(n + 1, 0, (x, y) => x + y);
			}

			for (int i = 0; i < n; i++) {
				var c = s[i] - 'a';
				segs[c].Update(i + 1, n + 1, 1);
			}

			var sb = new StringBuilder();
			for (int i = 0; i < q; i++) {
				int qq = cin.Int();
				if (qq == 1) {
					int ii = cin.Int() - 1;
					char c = (char)(cin.Next()[0] - 'a');
					if (ss[ii] != c) {
						int c2 = ss[ii];
						ss[ii] = c;
						segs[c2].Update(ii + 1, n + 1, -1);
						segs[c].Update(ii + 1, n + 1, 1);
					}
				} else {
					int l = cin.Int() - 1;
					int r = cin.Int();
					int cnt = 0;
					for (int j = 0; j < 26; j++) {
						if (segs[j].Query(r) - segs[j].Query(l) > 0) {
							cnt++;
						}
					}

					sb.AppendLine(cnt.ToString());
				}
			}

			Console.WriteLine(sb.ToString());
		}
	}

	public class LazySegmentTree<T>
	{
		private readonly int n_;
		private readonly T unit_;
		private readonly T[] tree_;
		private readonly bool[] should_;
		private readonly Func<T, T, T> merge_;

		public int Count { get; }

		public LazySegmentTree(int count, T unit, Func<T, T, T> merge)
		{
			merge_ = merge;
			unit_ = unit;

			Count = count;
			n_ = 1;
			while (n_ < count) {
				n_ <<= 1;
			}

			tree_ = new T[n_ << 1];
			should_ = new bool[n_ << 1];
			for (int i = 0; i < tree_.Length; i++) {
				tree_[i] = unit;
			}
		}

		public T this[int i]
		{
			get { return Query(i); }
		}

		public void Update(int left, int right, T item)
		{
			UpdateCore(left, right, 1, 0, n_, item);
		}

		public T Query(int i)
		{
			int l = 0;
			int r = n_;
			int k = 1;
			while (r - l > 1) {
				Evaluate(k, l, r);
				int m = (l + r) / 2;
				if (i < m) {
					r = m;
					k = k << 1;
				} else {
					l = m;
					k = (k << 1) + 1;
				}
			}

			return tree_[k];
		}

		private void Evaluate(int k, int l, int r)
		{
			if (should_[k]) {
				if (r - l > 1) {
					tree_[k << 1] = merge_(tree_[k << 1], tree_[k]);
					should_[k << 1] = true;
					tree_[(k << 1) + 1] = merge_(tree_[(k << 1) + 1], tree_[k]);
					should_[(k << 1) + 1] = true;
					tree_[k] = unit_;
				}

				should_[k] = false;
			}
		}

		private void UpdateCore(int left, int right, int k, int l, int r, T item)
		{
			Evaluate(k, l, r);
			if (r <= left || right <= l) {
				return;
			}

			if (left <= l && r <= right) {
				tree_[k] = merge_(tree_[k], item);
				should_[k] = true;
				Evaluate(k, l, r);
				return;
			}

			UpdateCore(left, right, k << 1, l, (l + r) / 2, item);
			UpdateCore(left, right, (k << 1) + 1, (l + r) / 2, r, item);
		}
	}

	public class Scanner2
	{
		private readonly char[] delimiter_ = new char[] { ' ' };
		private readonly string filePath_;
		private readonly Func<string> reader_;
		private string[] buf_;
		private int index_;

		public Scanner2(string file = "")
		{
			if (string.IsNullOrWhiteSpace(file)) {
				reader_ = Console.ReadLine;
			} else {
				filePath_ = file;
				var fs = new StreamReader(file);
				reader_ = fs.ReadLine;
			}
			buf_ = new string[0];
			index_ = 0;
		}

		public string Next()
		{
			if (index_ < buf_.Length) {
				return buf_[index_++];
			}

			string st = reader_();
			while (st == "") {
				st = reader_();
			}

			buf_ = st.Split(delimiter_, StringSplitOptions.RemoveEmptyEntries);
			if (buf_.Length == 0) {
				return Next();
			}

			index_ = 0;
			return buf_[index_++];
		}

		public int Int() => int.Parse(Next());
		public long Long() => long.Parse(Next());
		public double Double() => double.Parse(Next());

		public int[] ArrayInt(int N, int add = 0)
		{
			int[] Array = new int[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Int() + add;
			}
			return Array;
		}

		public long[] ArrayLong(int N, long add = 0)
		{
			long[] Array = new long[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Long() + add;
			}
			return Array;
		}

		public double[] ArrayDouble(int N, double add = 0)
		{
			double[] Array = new double[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Double() + add;
			}
			return Array;
		}

		public void Save(string text)
		{
			if (string.IsNullOrWhiteSpace(filePath_)) {
				return;
			}

			File.WriteAllText(filePath_ + "_output.txt", text);
		}
	}
}

Measured memory_bytes: 150044