import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.LongBinaryOperator;

public class Main {
    static void solve(MyScanner in, MyWriter out) {
        int n = in.nextInt();
        char[] s = in.nextCharArray(n);
        SegmentTree t = new SegmentTree(n, 0L, (a, b) -> a | b);
        for (int i = 0; i < n; i++) {
            t.update(i, 1L << (s[i] - 'a'));
        }
        int q = in.nextInt();
        for (int j = 0; j < q; j++) {
            int type = in.nextInt();
            if (type == 1) {
                int i = in.nextInt() - 1;
                char c = in.nextChar();
                t.update(i, 1L << (c - 'a'));
            } else {
                int l = in.nextInt() - 1;
                int r = in.nextInt();
                long bit = t.query(l, r);
                out.println(Long.bitCount(bit));
            }
        }
    }
    static final class SegmentTree {
        private final int length;
        final int innerLength;
        final long[] a;
        private final long identityElement;
        private final LongBinaryOperator op;

        SegmentTree(int length, long identityElement, LongBinaryOperator op) {
            this.length = length;

            innerLength = Integer.bitCount(length) == 1
                    ? length
                    : Integer.highestOneBit(length) << 1;

            a = new long[(innerLength << 1) - 1];
            Arrays.fill(a, identityElement);

            this.identityElement = identityElement;
            this.op = op;
        }
        static SegmentTree min(int length) {
            return new SegmentTree(length, Long.MAX_VALUE, Math::min);
        }
        static SegmentTree max(int length) {
            return new SegmentTree(length, Long.MIN_VALUE, Math::max);
        }
        static SegmentTree sum(int length) {
            return new SegmentTree(length, 0, Math::addExact);
        }
        void update(int index, long value) {
            if (index < 0 || index >= length) {
                throw new IndexOutOfBoundsException();
            }
            int j = innerLength + index - 1;
            a[j] = value;
            while (j > 0) {
                j = (j - 1) / 2;
                a[j] = op.applyAsLong(a[j * 2 + 1], a[j * 2 + 2]);
            }
        }
        private long _query(int from, int to, int index, int left, int right) {
            if (right <= from || to <= left) {
                return identityElement;
            }
            if (from <= left && right <= to) {
                return a[index];
            }
            int center = (left + right) >>> 1;
            return op.applyAsLong(_query(from, to, index * 2 + 1, left, center),
                                  _query(from,
                                         to,
                                         index * 2 + 2,
                                         center,
                                         right));
        }
        long query(int fromIndex, int toIndex) {
            if (fromIndex < 0 || toIndex > length || fromIndex > toIndex) {
                throw new IndexOutOfBoundsException();
            }
            return _query(fromIndex, toIndex, 0, 0, innerLength);
        }
    }
    public static void main(String[] args) {
        MyWriter w = new MyWriter(System.out);
        solve(new MyScanner(System.in), w);
        w.flush();
    }
    static final class MyScanner {
        static final int BUFFER_SIZE = 8192;
        private final InputStream in;
        private final byte[] buffer = new byte[BUFFER_SIZE];
        private int point;
        private int readLength;

        MyScanner(InputStream in) {
            this.in = in;
        }
        private byte readByte() {
            if (point < readLength) {
                byte result = buffer[point];
                point += 1;
                return result;
            }
            try {
                readLength = in.read(buffer);
            } catch (IOException e) {
                throw new AssertionError(null, e);
            }
            if (readLength == -1) {
                return -1;
            }
            point = 1;
            return buffer[0];
        }
        private static boolean isPrintableCharExceptSpace(byte c) {
            return 33 <= c && c <= 126;
        }
        public char nextChar() {
            byte c = readByte();
            while (!(c == -1 || isPrintableCharExceptSpace(c))) {
                c = readByte();
            }
            if (c == -1) {
                throw new NoSuchElementException();
            }
            return (char)c;
        }
        public String next() {
            return next(16);
        }
        public String next(int n) {
            byte c = readByte();
            while (!(c == -1 || isPrintableCharExceptSpace(c))) {
                c = readByte();
            }
            if (c == -1) {
                throw new NoSuchElementException();
            }
            StringBuilder b = new StringBuilder(n);
            do {
                b.append((char)c);
                c = readByte();
            } while (c != -1 && isPrintableCharExceptSpace(c));
            return b.toString();
        }
        public long nextLong() {
            byte c = readByte();
            while (!(c == -1 || isPrintableCharExceptSpace(c))) {
                c = readByte();
            }
            if (c == -1) {
                throw new NoSuchElementException();
            }
            boolean minus = false;
            if (c == '-') {
                minus = true;
                c = readByte();
            }
            long result = 0L;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                result = result * 10L + (c - '0');
                c = readByte();
            } while (c != -1 && isPrintableCharExceptSpace(c));
            return minus ? -result : result;
        }
        public int nextInt() {
            long n = nextLong();
            if (n < Integer.MIN_VALUE || n > Integer.MAX_VALUE) {
                throw new InputMismatchException();
            }
            return (int)n;
        }
        public double nextDouble() {
            return Double.parseDouble(next());
        }
        public int[] nextIntArray(int n) {
            int[] result = new int[n];
            for (int i = 0; i < n; i++) {
                result[i] = nextInt();
            }
            return result;
        }
        public long[] nextLongArray(int n) {
            long[] result = new long[n];
            for (int i = 0; i < n; i++) {
                result[i] = nextLong();
            }
            return result;
        }
        public char[] nextCharArray(int n) {
            char[] result = new char[n];
            for (int i = 0; i < n; i++) {
                result[i] = nextChar();
            }
            return result;
        }
        public char[][] next2dCharArray(int n, int m) {
            char[][] result = new char[n][m];
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    result[i][j] = nextChar();
                }
            }
            return result;
        }
        public int[][] nextVerticalIntArrays(int arrayCount, int arrayLength) {
            int[][] result = new int[arrayCount][arrayLength];
            for (int i = 0; i < arrayLength; i++) {
                for (int j = 0; j < arrayCount; j++) {
                    result[j][i] = nextInt();
                }
            }
            return result;
        }
        public long[][] nextVerticalLongArrays(int arrayCount,
                                               int arrayLength) {
            long[][] result = new long[arrayCount][arrayLength];
            for (int i = 0; i < arrayLength; i++) {
                for (int j = 0; j < arrayCount; j++) {
                    result[j][i] = nextLong();
                }
            }
            return result;
        }
        public char[][] nextVerticalCharArrays(int arrayCount,
                                               int arrayLength) {
            char[][] result = new char[arrayCount][arrayLength];
            for (int i = 0; i < arrayLength; i++) {
                for (int j = 0; j < arrayCount; j++) {
                    result[j][i] = nextChar();
                }
            }
            return result;
        }
    }
    static final class MyWriter extends PrintWriter {
        MyWriter(OutputStream out) {
            super(out);
        }
        public void joinAndPrintln(int[] x) {
            joinAndPrintln(x, " ");
        }
        public void joinAndPrintln(int[] x, String delimiter) {
            StringBuilder b = new StringBuilder();
            if (x.length > 0) {
                b.append(x[0]);
                for (int i = 1; i < x.length; i++) {
                    b.append(delimiter).append(x[i]);
                }
            }
            println(b.toString());
        }
        public void joinAndPrintln(long[] x) {
            joinAndPrintln(x, " ");
        }
        public void joinAndPrintln(long[] x, String delimiter) {
            StringBuilder b = new StringBuilder();
            if (x.length > 0) {
                b.append(x[0]);
                for (int i = 1; i < x.length; i++) {
                    b.append(delimiter).append(x[i]);
                }
            }
            println(b.toString());
        }
        public void joinAndPrintln(Iterable<?> iterable) {
            joinAndPrintln(iterable, " ");
        }
        public void joinAndPrintln(Iterable<?> iterable, String delimiter) {
            StringBuilder b = new StringBuilder();
            for (Iterator<?> i = iterable.iterator(); i.hasNext();) {
                b.append(i.next());
                while (i.hasNext()) {
                    b.append(delimiter).append(i.next());
                }
            }
            println(b.toString());
        }
    }
}


Measured memory_bytes: 36564