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(non_snake_case)]
#![allow(dead_code)]
#![allow(unused_macros)]
#![allow(unused_imports)]

use std::str::FromStr;
use std::io::*;
use std::collections::*;
use std::cmp::*;

struct Scanner<I: Iterator<Item = char>> {
    iter: std::iter::Peekable<I>,
}

macro_rules! exit {
    () => {{
        exit!(0)
    }};
    ($code:expr) => {{
        if cfg!(local) {
            writeln!(std::io::stderr(), "===== Terminated =====")
                .expect("failed printing to stderr");
        }
        std::process::exit($code);
    }}
}

impl<I: Iterator<Item = char>> Scanner<I> {
    pub fn new(iter: I) -> Scanner<I> {
        Scanner {
            iter: iter.peekable(),
        }
    }

    pub fn safe_get_token(&mut self) -> Option<String> {
        let token = self.iter
            .by_ref()
            .skip_while(|c| c.is_whitespace())
            .take_while(|c| !c.is_whitespace())
            .collect::<String>();
        if token.is_empty() {
            None
        } else {
            Some(token)
        }
    }

    pub fn token(&mut self) -> String {
        self.safe_get_token().unwrap_or_else(|| exit!())
    }

    pub fn get<T: FromStr>(&mut self) -> T {
        self.token().parse::<T>().unwrap_or_else(|_| exit!())
    }

    pub fn vec<T: FromStr>(&mut self, len: usize) -> Vec<T> {
        (0..len).map(|_| self.get()).collect()
    }

    pub fn mat<T: FromStr>(&mut self, row: usize, col: usize) -> Vec<Vec<T>> {
        (0..row).map(|_| self.vec(col)).collect()
    }

    pub fn char(&mut self) -> char {
        self.iter.next().unwrap_or_else(|| exit!())
    }

    pub fn chars(&mut self) -> Vec<char> {
        self.get::<String>().chars().collect()
    }

    pub fn mat_chars(&mut self, row: usize) -> Vec<Vec<char>> {
        (0..row).map(|_| self.chars()).collect()
    }

    pub fn line(&mut self) -> String {
        if self.peek().is_some() {
            self.iter
                .by_ref()
                .take_while(|&c| !(c == '\n' || c == '\r'))
                .collect::<String>()
        } else {
            exit!();
        }
    }

    pub fn peek(&mut self) -> Option<&char> {
        self.iter.peek()
    }
}

struct BinaryIndexedTree<T> {
    n: usize,
    bit: Vec<T>,
}

use std::ops::AddAssign;

impl<T: Copy + Default + AddAssign> BinaryIndexedTree<T> {
    fn new(n: usize) -> Self {
        BinaryIndexedTree {
            n: n + 1,
            bit: vec![T::default(); n + 1],
        }
    }

    fn add(&mut self, i: usize, v: T) {
        let mut cur = i+1;
        while cur < self.n {
            self.bit[cur] += v;
            cur += cur & (!cur+1);
        }
    }

    fn sum(&self, i: usize) -> T {
        let mut ret = T::default();
        let mut cur = i+1;
        while cur > 0 {
            ret += self.bit[cur];
            cur -= cur & (!cur+1);
        }
        ret
    }
}

fn main() {
    let cin = stdin();
    let cin = cin.lock();
    let mut sc = Scanner::new(cin.bytes().map(|c| c.unwrap() as char));
    let N: usize = sc.get();
    let Q: usize = sc.get();
    let c: Vec<usize> = sc.vec(N);
    let mut prev: Vec<Option<usize>> = vec![None; N+1];
    let mut ps: Vec<Vec<usize>> = vec![Vec::new(); N];
    for i in 0..N {
        if let Some(l) = prev[c[i]] {
            ps[l].push(i);
        }
        prev[c[i]] = Some(i);
    }
    let mut qs = vec![Vec::new(); N];
    for i in 0..Q {
        let l: usize = sc.get();
        let r: usize = sc.get();
        qs[l-1].push((i, r-1));
    }
    let mut bit = BinaryIndexedTree::new(N);
    let mut ans = vec![0; Q];
    for l in (0..N).rev() {
        for &r in &ps[l] {
            bit.add(r, 1);
        }
        for &(i, r) in &qs[l] {
            ans[i] = r - l + 1 - bit.sum(r);
        }
    }
    for i in 0..Q {
        println!("{}", ans[i]);
    }
}