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::Usize1;
use proconio::{fastout, input};

#[fastout]
fn main() {
    input! {
        n: usize,
        q: usize,
        ball: [Usize1; n],
        query: [(Usize1, Usize1); q],
    }
    let mut dup_index: Vec<Option<usize>> = vec![None; n];
    let mut ball_memo: Vec<Option<usize>> = vec![None; n];
    for (i, &b) in ball.iter().enumerate() {
        if let Some(di) = dup_index[b] {
            ball_memo[di] = Some(i);
        }
        dup_index[b] = Some(i);
    }

    let mut query_list = vec![Vec::with_capacity(q); n];
    for (i, (ql, qr)) in query.into_iter().enumerate() {
        query_list[ql].push((qr, i));
    }

    let mut res = vec![0; q];
    let mut bit = BIT::new(&vec![0; n]);
    for (ql, qvec) in query_list.into_iter().enumerate().rev() {
        if let Some(memo) = ball_memo[ql] {
            bit.add(memo, 1);
        }
        for (qr, i) in qvec {
            res[i] = (qr - ql + 1) - bit.sum(qr);
        }
    }
    for r in res {
        println!("{}", r);
    }
}

// BIT

use num_traits::{NumOps, Zero};
use std::marker::Copy;

pub struct BIT<T> {
    tree: Vec<T>,
}

impl<T> BIT<T>
where
    T: Copy + NumOps + Zero,
{
    pub fn new(data: &[T]) -> Self {
        let size = data.len();
        let mut bit = BIT {
            tree: vec![T::zero(); size],
        };
        for (i, &x) in data.iter().enumerate() {
            bit.add(i, x);
        }
        bit
    }

    pub fn size(&self) -> usize {
        self.tree.len()
    }

    pub fn add(&mut self, i: usize, x: T) {
        let size = self.size();
        let mut i = i;
        while i < size {
            self.tree[i] = self.tree[i] + x;
            i += (i + 1) & (!(i + 1)).wrapping_add(1);
        }
    }

    pub fn sum(&self, i: usize) -> T {
        let mut res = T::zero();
        let mut i = i as isize;
        while i >= 0 {
            res = res + self.tree[i as usize];
            i -= (i + 1) & -(i + 1);
        }
        res
    }
}