Problem:
Score : 600 points

Problem Statement

We have N colored balls arranged in a row from left to right; the color of the i-th ball from the left is c_i.

You are given Q queries. The i-th query is as follows: how many different colors do the l_i-th through r_i-th balls from the left have?

Constraints

1\leq N,Q \leq 5 \times 10^5

1\leq c_i \leq N

1\leq l_i \leq r_i \leq N

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N Q
c_1 c_2 \cdots c_N
l_1 r_1
l_2 r_2
:
l_Q r_Q

Output

Print Q lines. The i-th line should contain the response to the i-th query.

Sample Input 1

4 3
1 2 1 3
1 3
2 4
3 3

Sample Output 1

2
3
1

The 1-st, 2-nd, and 3-rd balls from the left have the colors 1, 2, and 1 - two different colors.

The 2-st, 3-rd, and 4-th balls from the left have the colors 2, 1, and 3 - three different colors.

The 3-rd ball from the left has the color 1 - just one color.

Sample Input 2

10 10
2 5 6 5 2 1 7 9 7 2
5 5
2 4
6 7
2 2
7 8
7 9
1 8
6 9
8 10
6 8

Sample Output 2

1
2
2
1
2
2
6
3
3
3

Solution in Java (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Objects;
import java.util.StringTokenizer;
import java.util.function.BiFunction;
import java.util.function.Function;

public class Main {

    static BiFunction<Integer, Integer, Integer> ADD = (x, y) -> (x + y);
    static BiFunction<ArrayList<Integer>, ArrayList<Integer>, ArrayList<Integer>> ADD_ARRAY_LIST = (x, y) -> {
        x.addAll(y);
        return x;
    };

    static Function<Pair<Integer, Integer>, Integer> GET_FIRST = (x) -> (x.first);
    static Function<Pair<Integer, Integer>, Integer> GET_SECOND = (x) -> (x.second);
    static Comparator<Pair<Integer, Integer>> C = Comparator.comparing(GET_FIRST).thenComparing(GET_SECOND);

    public static void main(String[] args) throws Exception {
        long startTime = System.nanoTime();
        int t = 1;
        while (t-- > 0) {
            solve();
        }
        long endTime = System.nanoTime();
        err.println("Execution Time : +" + (endTime - startTime) / 1000000 + " ms");
        exit(0);
    }

    static void solve() {
        int N = in.nextInt();
        int M = 2 * 1000000 + 1;
        int Q = in.nextInt();
        ArrayList<Pair<Integer, Integer>>[] queries = new ArrayList[M + 10];
        for (int i = 0; i <= M; i++) {
            queries[i] = new ArrayList<>();
        }
        int[] colors = new int[M];
        int[] previous_position = new int[M];
        int[] current_position = new int[M];
        int[] ans = new int[M];
        for (int i = 1; i <= N; i++) {
            colors[i] = in.nextInt();
            previous_position[i] = current_position[colors[i]];
            current_position[colors[i]] = i;
        }
        for (int i = 1; i <= Q; i++) {
            int l = in.nextInt();
            int r = in.nextInt();
            queries[r].add(make_pair(l, i));
        }
        Seg.build();
        for (int i = 1; i <= N; i++) {
            Seg.upd(1, 1, N, previous_position[i] + 1, i, 1);
            for (Pair<Integer, Integer> c : queries[i]) {
                ans[c.second] = Seg.qry(1, 1, N, c.first);
            }
        }
        for (int i = 1; i <= Q; i++) {
            out.println(ans[i] + " ");
        }
    }

    // Range update with query at pos.
    static class Seg {
        static int[] lz;

        static void build() {
            lz = new int[2 * 100000 + 1];
        }

        static void push(int id) {
            lz[id * 2] += lz[id];
            lz[id * 2 + 1] += lz[id];
            lz[id] = 0;
        }

        static void upd(int id, int l, int r, int ql, int qr, int v) {
            if (l > qr || r < ql) {
                return;
            }
            if (ql <= l && r <= qr) {
                lz[id] += v;
                return;
            }
            push(id);
            int mid = (l + r) / 2;
            upd(id * 2, l, mid, ql, qr, v);
            upd(id * 2 + 1, mid + 1, r, ql, qr, v);
        }

        static int qry(int id, int l, int r, int p) {
            if (l == r) {
                return lz[id];
            }
            push(id);
            int mid = (l + r) / 2;
            if (p <= mid) {
                return qry(id * 2, l, mid, p);
            } else {
                return qry(id * 2 + 1, mid + 1, r, p);
            }
        }
    }

    static void debug(Object... args) {
        for (Object a : args) {
            out.println(a);
        }
    }

    static void y() {
        out.println("YES");
    }

    static void n() {
        out.println("NO");
    }

    static <T> T min(T a, T b, Comparator<T> C) {
        if (C.compare(a, b) <= 0) {
            return a;
        }
        return b;
    }

    static <T> T max(T a, T b, Comparator<T> C) {
        if (C.compare(a, b) >= 0) {
            return a;
        }
        return b;
    }

    static void fail() {
        out.println("-1");
    }

    static class Pair<T, R> {
        public T first;
        public R second;

        public Pair(T first, R second) {
            this.first = first;
            this.second = second;
        }

        @Override
        public boolean equals(final Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            final Pair<?, ?> pair = (Pair<?, ?>) o;
            return Objects.equals(first, pair.first) && Objects.equals(second, pair.second);
        }

        @Override
        public int hashCode() {
            return Objects.hash(first, second);
        }

        @Override
        public String toString() {
            return "Pair{" + "a=" + first + ", b=" + second + '}';
        }

        public T getFirst() {
            return first;
        }

        public R getSecond() {
            return second;
        }
    }

    static <T, R> Pair<T, R> make_pair(T a, R b) {
        return new Pair<>(a, b);
    }

    static class ArrayUtils {

        static void swap(int[] a, int i, int j) {
            int temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }

        static void swap(char[] a, int i, int j) {
            char temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }

        static void print(char[] a) {
            for (char c : a) {
                out.print(c);
            }
            out.println("");
        }

        static int[] reverse(int[] data) {
            int[] p = new int[data.length];
            for (int i = 0, j = data.length - 1; i < data.length; i++, j--) {
                p[i] = data[j];
            }
            return p;
        }

        static void prefixSum(long[] data) {
            for (int i = 1; i < data.length; i++) {
                data[i] += data[i - 1];
            }
        }

        static void prefixSum(int[] data) {
            for (int i = 1; i < data.length; i++) {
                data[i] += data[i - 1];
            }
        }

        static long[] reverse(long[] data) {
            long[] p = new long[data.length];
            for (int i = 0, j = data.length - 1; i < data.length; i++, j--) {
                p[i] = data[j];
            }
            return p;
        }

        static char[] reverse(char[] data) {
            char[] p = new char[data.length];
            for (int i = 0, j = data.length - 1; i < data.length; i++, j--) {
                p[i] = data[j];
            }
            return p;
        }

        static int[] MergeSort(int[] A) {
            if (A.length > 1) {
                int q = A.length / 2;
                int[] left = new int[q];
                int[] right = new int[A.length - q];
                System.arraycopy(A, 0, left, 0, q);
                System.arraycopy(A, q, right, 0, A.length - q);
                int[] left_sorted = MergeSort(left);
                int[] right_sorted = MergeSort(right);
                return Merge(left_sorted, right_sorted);
            } else {
                return A;
            }
        }

        static int[] Merge(int[] left, int[] right) {
            int[] A = new int[left.length + right.length];
            int i = 0;
            int j = 0;
            for (int k = 0; k < A.length; k++) {
                // To handle left becoming empty
                if (i == left.length && j < right.length) {
                    A[k] = right[j];
                    j++;
                    continue;
                }
                // To handle right becoming empty
                if (j == right.length && i < left.length) {
                    A[k] = left[i];
                    i++;
                    continue;
                }
                if (left[i] <= right[j]) {
                    A[k] = left[i];
                    i++;
                } else {
                    A[k] = right[j];
                    j++;
                }
            }
            return A;
        }

        static long[] MergeSort(long[] A) {
            if (A.length > 1) {
                int q = A.length / 2;
                long[] left = new long[q];
                long[] right = new long[A.length - q];
                System.arraycopy(A, 0, left, 0, q);
                System.arraycopy(A, q, right, 0, A.length - q);
                long[] left_sorted = MergeSort(left);
                long[] right_sorted = MergeSort(right);
                return Merge(left_sorted, right_sorted);
            } else {
                return A;
            }
        }

        static long[] Merge(long[] left, long[] right) {
            long[] A = new long[left.length + right.length];
            int i = 0;
            int j = 0;
            for (int k = 0; k < A.length; k++) {
                // To handle left becoming empty
                if (i == left.length && j < right.length) {
                    A[k] = right[j];
                    j++;
                    continue;
                }
                // To handle right becoming empty
                if (j == right.length && i < left.length) {
                    A[k] = left[i];
                    i++;
                    continue;
                }
                if (left[i] <= right[j]) {
                    A[k] = left[i];
                    i++;
                } else {
                    A[k] = right[j];
                    j++;
                }
            }
            return A;
        }
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 2048);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public int[] readAllInts(int n) {
            int[] p = new int[n];
            for (int i = 0; i < n; i++) {
                p[i] = in.nextInt();
            }
            return p;
        }

        public int[] readAllInts(int n, int s) {
            int[] p = new int[n + s];
            for (int i = s; i < n + s; i++) {
                p[i] = in.nextInt();
            }
            return p;
        }

        public long[] readAllLongs(int n) {
            long[] p = new long[n];
            for (int i = 0; i < n; i++) {
                p[i] = in.nextLong();
            }
            return p;
        }

        public long[] readAllLongs(int n, int s) {
            long[] p = new long[n + s];
            for (int i = s; i < n + s; i++) {
                p[i] = in.nextLong();
            }
            return p;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }

    static void exit(int a) {
        out.close();
        err.close();
        System.exit(a);
    }

    static InputStream inputStream = System.in;
    static OutputStream outputStream = System.out;
    static OutputStream errStream = System.err;
    static InputReader in = new InputReader(inputStream);
    static PrintWriter out = new PrintWriter(outputStream);
    static PrintWriter err = new PrintWriter(errStream);
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

}