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

pub trait MoOperator {
    type Value;
    type Query;
    type Answer;
    fn init(&mut self);
    fn insert(&mut self, v: &Self::Value);
    fn delete(&mut self, v: &Self::Value);
    fn answer(&mut self, q: Self::Query) -> Self::Answer;
    fn solve(&mut self, array: &[Self::Value], mut query: Vec<(usize, usize, Self::Query)>, answer: &mut [Self::Answer]) {
        let state = self;
        let size = array.len();
        assert!(query.len() <= answer.len());
        assert!(query.iter().all(|p| p.0 < p.1 && p.1 <= size));
        if query.is_empty() {
            return;
        }
        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 array[min(x, l)..x].iter().rev() {
                    state.insert(v);
                    x = l;
                }
                for v in array[min(y, r)..r].iter() {
                    state.insert(v);
                    y = r;
                }
                for v in array[min(x, l)..l].iter() {
                    state.delete(v);
                    x = l;
                }
                for v in array[min(y, r)..y].iter().rev() {
                    state.delete(v);
                    y = r;
                }
                answer[k] = state.answer(op);
            }
        }
    }
}

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

impl MoOperator for State {
    type Value = usize;
    type Query = ();
    type Answer = usize;
    fn init(&mut self) {
        for c in self.cnt.iter_mut() {
            *c = 0;
        }
        self.ans = 0;
    }
    fn insert(&mut self, x: &Self::Value) {
        let c = &mut self.cnt[*x];
        if *c == 0 {
            self.ans += 1;
        }
        *c += 1;
    }
    fn delete(&mut self, x: &Self::Value) {
        let c = &mut self.cnt[*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 ask: Vec<_> = ask.into_iter().map(|(l, r)| (l, r, ())).collect();
    let mut ans = vec![0; q];
    State {
        cnt: vec![0; n],
        ans: 0,
    }.solve(&c, ask, &mut ans);
    for a in ans {
        println!("{}", a);
    }
}

fn main() {
    run();
}