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

class Program
{
    static void Main(string[] args)
    {
        var N = sc.ReadInt();
        var S = sc.ReadStr().ToArray();
        var bit = new BinaryIndexedTree[26];
        for (int i = 0; i < 26; i++) bit[i] = new BinaryIndexedTree(N);
        for (int i = 0; i < N; i++)
        {
            bit[S[i] - 'a'].Add(i + 1, 1);
        }

        var list = new List<long>();
        var Q = sc.ReadInt();
        for (int _ = 0; _ < Q; _++)
        {
            var command = sc.ReadInt();
            if (command == 1)
            {
                // 更新
                var i = sc.ReadInt() - 1;
                var c = sc.ReadChar();
                var prev = S[i] - 'a';
                bit[prev].Add(i + 1, -1);
                bit[c - 'a'].Add(i + 1, 1);
                S[i] = c;
            }
            else
            {
                // 計算
                var l = sc.ReadInt();
                var r = sc.ReadInt();
                var ans = 0L;
                for (int i = 0; i < 26; i++)
                {
                    var sum = bit[i].Sum(r);
                    if (l > 1) sum -= bit[i].Sum(l - 1);
                    if (sum > 0) ans++;
                }
                list.Add(ans);
            }
        }
        foreach (var item in list)
        {
            Console.WriteLine(item);
        }
    }

    class BinaryIndexedTree
    {
        public int N { get; set; }
        public long[] Array { get; set; }
        public BinaryIndexedTree(int n)
        {
            this.N = n;
            this.Array = new long[N + 1];
        }
        public void Add(int index, long value)
        {
            while (index <= this.N)
            {
                this.Array[index] += value;
                index += index & (-index);
            }
        }
        public long Sum(int l, int r)
        {
            return this.Sum(r) - this.Sum(l);
        }
        public long Sum(int index)
        {
            var sum = 0L;
            while (index > 0)
            {
                sum += this.Array[index];
                index -= index & (-index);
            }
            return sum;
        }
    }
    static Scanner sc = new Scanner();
}

class Scanner
{
    string[] S = new string[0];
    int Index = 0;
    char[] Separators = new char[] { ' ' };

    public string Next()
    {
        if (this.Index < this.S.Length) return this.S[this.Index++];
        var line = "";
        while (line == "") line = Console.ReadLine();
        this.S = line.Split(this.Separators, StringSplitOptions.RemoveEmptyEntries);
        if (this.S.Length == 0) return this.Next();
        this.Index = 0;
        return this.S[this.Index++];
    }
    public string ReadStr()
    {
        return this.Next();
    }
    public char ReadChar()
    {
        return this.Next()[0];
    }
    public int ReadInt()
    {
        return int.Parse(this.Next());
    }
    public uint ReadUInt()
    {
        return uint.Parse(this.Next());
    }
    public long ReadLong()
    {
        return long.Parse(this.Next());
    }
    public double ReadDouble()
    {
        return double.Parse(this.Next());
    }
    public Tuple<int, int> ReadTup(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<long, long> ReadTupLong(int add = 0)
    {
        return Tuple.Create(this.ReadLong() + add, this.ReadLong() + add);
    }
    public Tuple<int, int, int> ReadTup3(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public Tuple<int, int, int, int> ReadTup4(int add = 0)
    {
        return Tuple.Create(this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add, this.ReadInt() + add);
    }
    public int[] ReadIntArray(int n)
    {
        var array = new int[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadInt();
        }
        return array;
    }
    public long[] ReadLongArray(int n)
    {
        var array = new long[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadLong();
        }
        return array;
    }
    public double[] ReadDoubleArray(int n)
    {
        var array = new double[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadDouble();
        }
        return array;
    }
    public char[] ReadCharArray(int n)
    {
        var array = new char[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadChar();
        }
        return array;
    }
    public string[] ReadStrArray(int n)
    {
        var array = new string[n];
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = this.ReadStr();
        }
        return array;
    }
    public Tuple<long, long>[] ReadTupLongArray(int n, int add = 0)
    {
        var array = new Tuple<long, long>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTupLong(add);
        }
        return array;
    }
    public Tuple<int, int>[] ReadTupArray(int n, int add = 0)
    {
        var array = new Tuple<int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup(add);
        }
        return array;
    }
    public Tuple<int, int, int>[] ReadTup3Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup3(add);
        }
        return array;
    }
    public Tuple<int, int, int, int>[] ReadTup4Array(int n, int add = 0)
    {
        var array = new Tuple<int, int, int, int>[n];
        for (int i = 0; i < n; i++)
        {
            array[i] = this.ReadTup4(add);
        }
        return array;
    }
}


Measured memory_bytes: 121064