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::{fastout, input};

use proconio::marker::Usize1;

struct FenwickTree {
    seg: Vec<i64>,
}

impl FenwickTree {
    fn new(n: usize) -> Self {
        FenwickTree {
            seg: vec![0; n + 1],
        }
    }
    fn len(&self) -> usize {
        self.seg.len() - 1
    }
    fn add(&mut self, i: usize, x: i64) {
        let mut i = i + 1;
        while i <= self.len() {
            self.seg[i] += x;
            i += i & -(i as isize) as usize;
        }
    }
    fn sum(&self, i: usize) -> i64 {
        let mut s = 0;
        let mut i = i;
        while i > 0 {
            s += self.seg[i];
            i -= i & -(i as isize) as usize;
        }
        s
    }
}

#[fastout]
fn main() {
    input! {
        n: usize, q: usize,
        cc: [Usize1; n],
        lr: [(Usize1, Usize1); q],
    }
    let mut ft = FenwickTree::new(n);
    let mut ls = vec![None; n];
    let mut ilr = lr.into_iter().enumerate().collect::<Vec<_>>();
    ilr.sort_by_key(|&(_i, (_l, r))| r);
    let mut ans = vec![0; q];
    let mut j = 0;
    for i in 0..n {
        let c = cc[i];
        if let Some(i) = ls[c] {
            ft.add(i, -1);
        }
        ls[c] = Some(i);
        ft.add(i, 1);
        while j < q && (ilr[j].1).1 <= i {
            ans[ilr[j].0] = ft.sum((ilr[j].1).1 + 1) - ft.sum((ilr[j].1).0);
            j += 1;
        }
    }
    for a in ans {
        println!("{}", a);
    }
}