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 Rust (1.42.0) (judge verdict: Accepted)

use proconio::marker::*;
use proconio::*;
use std::cmp::*;

pub trait MoOperator {
    type Query;
    type Answer;
    fn size(&self) -> usize;
    fn init(&mut self);
    fn insert(&mut self, v: usize);
    fn delete(&mut self, v: usize);
    fn answer(&mut self, q: Self::Query) -> Self::Answer;
}

struct State {
    c: Vec<usize>,
    cnt: Vec<u32>,
    ans: usize,
}

impl MoOperator for State {
    type Query = ();
    type Answer = usize;
    fn size(&self) -> usize {
        self.c.len()
    }
    fn init(&mut self) {
        for c in self.cnt.iter_mut() {
            *c = 0;
        }
        self.ans = 0;
    }
    fn insert(&mut self, x: usize) {
        let c = &mut self.cnt[self.c[x]];
        if *c == 0 {
            self.ans += 1;
        }
        *c += 1;
    }
    fn delete(&mut self, x: usize) {
        let c = &mut self.cnt[self.c[x]];
        if *c == 1 {
            self.ans -= 1;
        }
        *c -= 1;
    }
    fn answer(&mut self, _q: Self::Query) -> usize {
        self.ans
    }
}

#[fastout]
fn run() {
    input! {
        n: usize,
        q: usize,
        c: [Usize1; n],
        ask: [(Usize1, usize); q],
    }
    let mut query: Vec<_> = ask.into_iter().map(|(l, r)| (l, r, ())).collect();
    let mut answer = vec![0; q];
    let mut state = State {
        c: c,
        cnt: vec![0; n],
        ans: 0,
    };
    let size = n;
    let batch = (size as f64 / (query.len() as f64).sqrt()).ceil() as usize;
    let mut q = vec![];
    std::mem::swap(&mut q, &mut query);
    let mut query = (0..(size / batch + 1)).map(|_| vec![]).collect::<Vec<_>>();
    for (i, (l, r, op)) in q.into_iter().enumerate() {
        query[l / batch].push((r, l, i, op));
    }
    state.init();
    let mut x = 0;
    let mut y = 0;
    for (i, mut query) in query.into_iter().enumerate() {
        query.sort_unstable_by_key(|p| p.0);
        if i & 1 == 1 {
            query.reverse();
        }
        for (r, l, k, op) in query.into_iter() {
            for v in (min(x, l)..x).rev() {
                state.insert(v);
                x = l;
            }
            for v in min(y, r)..r {
                state.insert(v);
                y = r;
            }
            for v in min(x, l)..l {
                state.delete(v);
                x = l;
            }
            for v in (min(y, r)..y).rev() {
                state.delete(v);
                y = r;
            }
            answer[k] = state.answer(op);
        }
    }
    for a in answer {
        println!("{}", a);
    }
}

fn main() {
    run();
}