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 11.0.6) (judge verdict: Accepted)

/*
    Author: Anthony Ngene
    Created: 06/08/2020 - 06:41
*/

import java.io.*;
import java.util.*;

public class Main {
    // It takes a great deal of courage to stand up to your enemies, but even more to stand up to your friends. - J. K. Rowling
    public static void main(String[] args) throws IOException {
        in = new FastScanner();

        int n = in.intNext(), Q = in.intNext();
        int[] arr = in.nextIntArray(n);
        HashMap<Integer, ArrayList<int[]>> ends = new HashMap<>();
        for (int i = 0; i < Q; i++) {
            int[] node = new int[]{in.intNext(), in.intNext(), i};
            if (!ends.containsKey(node[1])) ends.put(node[1], new ArrayList<>());
            ends.get(node[1]).add(node);
        }

        long[] answers = new long[Q];
        HashMap<Integer, Integer> lastIdx = new HashMap<>();
        BIT fenwick = new BIT(n);
        for (int i = 1; i < n + 1; i++) {
            int num = arr[i - 1];
            if (lastIdx.containsKey(num)) {
                fenwick.update(lastIdx.get(num), -1);
            }
            lastIdx.put(num, i);
            fenwick.update(i, 1);
//            out.println(Arrays.toString(fenwick.tree));

            if (ends.containsKey(i)) {
                for (int[] node : ends.get(i)) {
                    answers[node[2]] = fenwick.rangeSum(node[0], node[1]);
                }
            }
        }
        for (long ans: answers) out.println(ans);

        out.close();
    }

    static class BIT {
        int[] tree;
        int n;
        int[] arr;

        public BIT(int n) {
            tree = new int[n + 1];
            this.n = n;
        }
        public BIT(int[] arr) {
            this.arr = arr;
            this.n = arr.length;
            tree = new int[n + 1];
            for (int i = 1; i < n + 1; i++) {
                tree[i] += arr[i-1];
                int parent = i + (i & -i);
                if (parent <= n) tree[parent] += tree[i];
            }
        }

        public long getSum(int idx) {
            // one indexed
            long total = 0;
            while (idx > 0) {
                total += tree[idx];
                idx = idx - (idx & -idx);
            }
            return total;
        }

        public long rangeSum(int a, int b) {
            // a-b inclusive: b > a and one indexed.
            return getSum(b) - getSum(a - 1);
        }

        public void update(int idx, int valueToAdd) {
            // one indexed
            while (idx <= n) {
                tree[idx] += valueToAdd;
                idx = idx + (idx & -idx);
            }
        }
    }


private static final FastWriter out = new FastWriter();
private static FastScanner in;
static ArrayList<Integer>[] adj;
private static long e97 = (long)1e9 + 7;
static class FastWriter {
    private static final int IO_BUFFERS = 128 * 1024;
    private final StringBuilder out;
    public FastWriter() {
        out = new StringBuilder(IO_BUFFERS);
    }
    public FastWriter p(Object object) {
        out.append(object);
        return this;
    }
    public FastWriter p(String format, Object... args) {
        out.append(String.format(format, args));
        return this;
    }
    public FastWriter pp(Object... args) {
        for (Object ob : args) {
            out.append(ob).append(" ");
        }
        out.append("\n");
        return this;
    }
    public FastWriter println(Object object) {
        out.append(object).append("\n");
        return this;
    }
    public void toFile(String fileName) throws IOException {
        BufferedWriter writer = new BufferedWriter(new FileWriter(fileName));
        writer.write(out.toString());
        writer.close();
    }
    public void close() throws IOException {
        System.out.print(out);
    }
}
static class FastScanner {
    private InputStream sin = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    public FastScanner(){}
    public FastScanner(String filename) throws FileNotFoundException {
        File file = new File(filename);
        sin = new FileInputStream(file);
    }
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = sin.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long longNext() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b) || b == ':'){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int intNext() {
        long nl = longNext();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double doubleNext() { return Double.parseDouble(next());}
    public long[] nextLongArray(final int n){
        final long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = longNext();
        return a;
    }
    public int[] nextIntArray(final int n){
        final int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = intNext();
        return a;
    }
    public ArrayList<Integer>[] getAdj(int n) {
        ArrayList<Integer>[] adj = new ArrayList[n + 1];
        for (int i = 1; i <= n; i++) adj[i] = new ArrayList<>();
        return adj;
    }

    public ArrayList<Integer>[] adjacencyList(int n, int m) throws IOException {
        adj = getAdj(n);
        for (int i = 0; i < m; i++) {
            int a = intNext(), b = intNext();
            adj[a].add(b);
            adj[b].add(a);
        }
        return adj;
    }
}
}