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)

#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use itertools::Itertools;
use num_traits::clamp;
use ordered_float::OrderedFloat;
use proconio::{input, marker::*, fastout};
use superslice::*;

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

    let mut queries = lr.into_iter().enumerate().sorted_by_key(|&(_, (l, _))| Reverse(l)).collect_vec();

    let mut pairs = Vec::new();
    let mut prevs = vec![n; n];
    for (i, c) in (0..).zip(c) {
        if prevs[c] != n {
            pairs.push((prevs[c], i));
        }
        prevs[c] = i;
    }
    pairs.sort();

    let mut bit = BIT::new(n);
    let mut ans = vec![0; q];
    for (i, (l, r)) in queries {
        while let Some((l2, r2)) = pairs.pop() {
            if l2 < l {
                pairs.push((l2, r2));
                break;
            }
            bit.add(r2+1, 1);
        }
        ans[i] = r + 1 - l - bit.sum(r+1);
    }

    for ans in ans {
        println!("{}", ans);
    }
}

#[allow(dead_code)]
/// Binary Indexed Tree of usize
pub struct BIT {
    buf: Vec<usize>,
}
#[allow(dead_code)]
impl BIT {
    pub fn new(n: usize) -> BIT {
        BIT {
            buf: vec![0; n + 1],
        }
    }
    pub fn sum(&self, i: usize) -> usize {
        let mut i = i;
        let mut s = 0;
        while i > 0 {
            s += self.buf[i];
            i &= i - 1;
        }
        s
    }
    pub fn add(&mut self, i: usize, x: usize) {
        let mut i = i as i64;
        while i < self.buf.len() as i64 {
            self.buf[i as usize] += x;
            i += i & -i;
        }
    }
}