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 itertools::Itertools;
use proconio::{input, marker::Usize1};

fn main() {
    input! {
        n: usize, q: usize,
        c: [Usize1; n],
        query: [(Usize1, Usize1); q]
    }

    let mut right = vec![None; n];
    let mut fw = Fenwick::new(n);

    let query = query.iter().enumerate().sorted_by_key(|(_, (_, r))| r);
    let mut ans = vec![0; q];
    let mut cur = 0;
    for (i, &(l, r)) in query {
        while cur <= r {
            if let Some(old) = right[c[cur]] {
                fw.add(old, -1);
            }
            right[c[cur]] = Some(cur);
            fw.add(cur, 1);
            cur += 1;
        }
        ans[i] = fw.sum(l, r + 1);
    }

    ans.iter().for_each(|it| println!("{}", it));
}

struct Fenwick(Vec<i64>);

impl Fenwick {
    fn new(n: usize) -> Self {
        Self(vec![0; n + 1])
    }
    fn sum(&self, l: usize, mut r: usize) -> i64 {
        if l != 0 {
            return self.sum(0, r) - self.sum(0, l);
        }
        let mut ret = 0;
        while r > 0 {
            ret += self.0[r];
            let ir = r as isize;
            r -= (ir & -ir) as usize;
        }
        ret
    }
    fn add(&mut self, mut i: usize, x: i64) {
        i += 1;
        while i < self.0.len() {
            self.0[i] += x;
            let ii = i as isize;
            i += (ii & -ii) as usize;
        }
    }
}