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,
  unused_variables,
  unused_assignments,
  unused_mut,
  unused_imports,
  unused_macros,
  dead_code
)]
//use proconio::fastout;
use proconio::{input, marker::*};
use std::cmp::*;
use std::collections::*;
//use std::collections::VecDeque;

macro_rules! debug {
  ($($a:expr),* $(,)*) => {
      #[cfg(debug_assertions)]
      eprintln!(concat!($("| ", stringify!($a), "={:?} "),*, "|"), $(&$a),*);
  };
}

fn main() {
  input! {
     N:usize,Q:usize,
     c:[Usize1;N],
     lr:[(Usize1,Usize1);Q]
  }
  let inf = std::usize::MAX;
  let c: Vec<usize> = c;
  let lr: Vec<(usize, usize)> = lr;
  let mut ans = vec![0; Q];
  let mut last = vec![inf; N];
  let mut next = vec![vec![]; N];
  for i in 0..N {
    let v = last[c[i]];
    if v != inf {
      next[v as usize].push(i);
    }
    last[c[i]] = i;
  }
  let mut qs = vec![Vec::with_capacity(N); N];
  for qi in 0..Q {
    debug!(lr);
    //(qi, &(l, r)) in lr.iter().enumerate() {
    let (l, r) = lr[qi];
    qs[l].push((r, qi));
  }
  //println!("p{:?}", next);
  let mut bit = BIT::new(N);
  for x in (0..N).rev() {
    for &y in next[x].iter() {
      bit.add(y, 1usize);
    }
    //println!("prev={:?}", next);
    for &(r, qi) in qs[x].iter() {
      //println!("sum={}", bit.sum(r));
      ans[qi] = (r - x + 1) - bit.sum(r);
    }
  }

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

struct BIT<T> {
  n: usize,
  d: Vec<T>,
}
use num_traits::*;
impl<T: NumAssign + ToPrimitive + FromPrimitive + Copy> BIT<T> {
  fn new(n: usize) -> BIT<T> {
    BIT {
      n: n,
      d: vec![T::from_i64(0).unwrap(); n + 1],
    }
  }
  fn add(&mut self, index: usize, x: T) -> () {
    let mut i = (index + 1) as i64;
    while i <= self.n as i64 {
      self.d[i as usize] += x;
      i += i & -i;
    }
  }
  fn sum(&self, index: usize) -> T {
    let mut x = self.d[0];
    let mut i = (index + 1) as i64;
    while i > 0 {
      x += self.d[i as usize];
      i -= i & -i;
    }
    x
  }
  fn range(&self, l: usize, r: usize) -> T {
    // l 以上 r 未満の範囲のsum
    match (l, r) {
      (0, _) => self.sum(r - 1),
      _ => self.sum(r - 1) - self.sum(l - 1),
    }
  }
}