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 std::collections::HashMap;

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

    let mut lr = lr_bak.clone();
    lr.sort_by(|(_, a), (_, b)| a.cmp(b));

    let mut color = vec![-1; n];
    let mut bit = Bit::new(n+1);
    let mut map = HashMap::new();

    let mut idx = 0;
    for &(l, r) in lr.iter() {
        while idx < r {
            idx += 1;
            if color[c[idx-1]] != -1 {
                bit.add(color[c[idx-1]] as usize, -1);
            }
            bit.add(idx, 1);
            color[c[idx-1]] = idx as i32;
        }

        map.insert((l, r), bit.sum(r) - bit.sum(l-1));
    }

    for &(l, r) in lr_bak.iter() {
        println!("{}", map.get(&(l, r)).unwrap());
    }
}

struct Bit {
    data: Vec<i64>,
}

impl Bit {
    pub fn new(n: usize) -> Bit {
        Bit {
            data: vec![0; n+1],
        }
    }

    pub fn add(&mut self, idx: usize, x: i64) {
        let mut idx = idx as i32;
        while idx as usize <= self.data.len()-1 {
            self.data[idx as usize] += x;
            idx += idx & -idx;
        }
    }

    pub fn sum(&self, idx: usize) -> i64 {
        let mut ret = 0;
        let mut idx = idx as i32;
        while idx > 0 {
            ret += self.data[idx as usize];
            idx -= idx & -idx;
        }

        ret
    }
}