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)

// ---------- begin SegmentTree Point update Range query ----------
mod segment_tree {
    pub struct PURQ<T: Clone, F: Fn(T, T) -> T> {
        n: usize,
        a: Vec<T>,
        id: T,
        op: F,
    }
    #[allow(dead_code)]
    impl<T: Clone, F: Fn(T, T) -> T> PURQ<T, F> {
        pub fn new(n: usize, id: T, op: F) -> PURQ<T, F> {
            let mut k = 1;
            while k < n {
                k *= 2;
            }
            PURQ {
                n: k,
                a: vec![id.clone(); 2 * k],
                id: id,
                op: op,
            }
        }
        pub fn update(&mut self, x: usize, v: T) {
            let mut k = self.n + x;
            let a = &mut self.a;
            a[k] = v;
            k >>= 1;
            while k > 0 {
                a[k] = (self.op)(a[2 * k].clone(), a[2 * k + 1].clone());
                k >>= 1;
            }
        }
        pub fn update_tmp(&mut self, x: usize, v: T) {
            self.a[x + self.n] = v;
        }
        pub fn update_all(&mut self) {
            for k in (1..(self.n)).rev() {
                self.a[k] = (self.op)(self.a[2 * k].clone(), self.a[2 * k + 1].clone());
            }
        }
        pub fn find(&self, mut l: usize, mut r: usize) -> T {
            let mut p = self.id.clone();
            let mut q = self.id.clone();
            l += self.n;
            r += self.n;
            while l < r {
                if (l & 1) == 1 {
                    p = (self.op)(p, self.a[l].clone());
                    l += 1;
                }
                if (r & 1) == 1 {
                    r -= 1;
                    q = (self.op)(self.a[r].clone(), q);
                }
                l >>= 1;
                r >>= 1;
            }
            (self.op)(p, q)
        }
    }
}
// ---------- end SegmentTree Point update Range query ----------

use proconio::*;
use proconio::marker::*;

#[fastout]
fn run() {
    input! {
        n: usize,
        q: usize,
        c: [Usize1; n],
        ask: [(Usize1, usize); q],
    }
    let mut a = vec![vec![]; n];
    for (i, &c) in c.iter().enumerate() {
        a[c].push(i);
    }
    let mut seg = segment_tree::PURQ::new(n, 0, |a, b| a + b);
    for a in a.iter_mut() {
        a.reverse();
        if let Some(k) = a.pop() {
            seg.update(k, 1);
        }
    }
    let mut query = vec![vec![]; n];
    for (i, (l, r)) in ask.into_iter().enumerate() {
        query[l].push((r, i));
    }
    let mut ans = vec![0; q];
    for (l, (query, c)) in query.into_iter().zip(c.into_iter()).enumerate() {
        for &(r, k) in query.iter() {
            ans[k] = seg.find(l, r);
        }
        seg.update(l, 0);
        if let Some(k) = a[c].pop() {
            seg.update(k, 1);
        }
    }
    for a in ans {
        println!("{}", a);
    }
}

fn main() {
    run();
}