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)

//  ____            _                  _                       _       _
// |  _ \ _   _ ___| |_    ___ _ __   | |_ ___ _ __ ___  _ __ | | __ _| |_ ___
// | |_) | | | / __| __|  / __| '_ \  | __/ _ \ '_ ` _ \| '_ \| |/ _` | __/ _ \
// |  _ <| |_| \__ \ |_  | (__| |_) | | ||  __/ | | | | | |_) | | (_| | ||  __/
// |_| \_\\__,_|___/\__|  \___| .__/___\__\___|_| |_| |_| .__/|_|\__,_|\__\___|
//                            |_| |_____|               |_|

//https://github.com/manta1130/Competitive_Programming_Template_Rust

mod  binary_indexed_tree{

type VecType = isize;

///Binary Indexed Tree
pub struct BIT {
    v: Vec<VecType>,
}

impl BIT {
    ///BIT木を構築する。
    ///
    ///n:要素数
    pub fn new(n: usize) -> BIT {
        let v = vec![0; n + 1];
        BIT { v: v }
    }

    ///任意の要素に値を加算する。
    ///
    /// index:加算する場所(0-indexed)
    /// value:加算する値
    pub fn add(&mut self, index: usize, value: VecType) {
        let mut i = (index + 1) as isize;
        while i <= (self.v.len() - 1) as isize {
            self.v[i as usize] += value;
            i += i & -i;
        }
    }

    ///[0,index]の区間和を求める。
    pub fn get(&mut self, index: usize) -> VecType {
        let mut i = (index + 1) as isize;
        let mut res = 0 as VecType;
        while i > 0 {
            res += self.v[i as usize];
            i -= i & -i;
        }
        res
    }
}
}

use binary_indexed_tree::*;
#[allow(unused_imports)]
use proconio::{
    fastout, input,
    marker::{Bytes, Chars, Isize1, Usize1},
};


#[fastout]
fn main() {
    input! {
        n:usize,q:usize,
        c:[usize;n]
    }
    let mut query = vec![];
    for i in 0..q {
        input! {l:Usize1,r:Usize1}
        query.push((l, r, i));
    }
    query.sort_by_key(|x| x.1);
    let mut p = 0;
    let mut ft = BIT::new(n);
    let mut table = vec![None; n + 1];
    let mut ans = vec![];
    for (l, r, i) in query {
        while r >= p {
            if let None = table[c[p]] {
                table[c[p]] = Some(p);
                ft.add(p, 1);
            } else {
                ft.add(table[c[p]].unwrap(), -1);
                table[c[p]] = Some(p);
                ft.add(p, 1);
            }
            p += 1;
        }
        ans.push((i, ft.get(r) - if l == 0 { 0 } else { ft.get(l - 1) }));
    }
    ans.sort();
    for (_, x) in ans {
        println!("{}", x);
    }
}