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: Wrong Answer)

use proconio::input;

struct BIT {
  n: usize,
  a: Vec<usize>,
}
impl BIT {
  fn new(size: usize) -> BIT {
    let n = size + 1;
    BIT {n, a: vec![0; n]}
  }
  
  fn add(&mut self, mut i: usize, x: usize) {
    while i < self.n {
      self.a[i] += x;
      i += ((i as isize) & -(i as isize)) as usize;
    }
  }
  
  fn sum(&self, mut i: usize) -> usize {
    let mut x = self.a[0];
    while i > 0 {
      x += self.a[i];
      i -= ((i as isize) & -(i as isize)) as usize;
    }
    x
  }
}

fn main() {
  input! {
    n: usize, q: usize,
    cs: [usize; n],
    queries: [(usize, usize); q],
  }
  
  let mut points: Vec<(usize, usize, usize)> = Vec::new();
  
  // O(N)
  let mut prevs = vec![None; n];
  for (i, &c) in cs.iter().enumerate() {
    if let Some(prev) = prevs[c-1] {
      points.push((n, prev, i));
    }
    prevs[c-1] = Some(i);
  }
  
  // O(Q)
  for (i, &(l, r)) in queries.iter().enumerate() {
    points.push((i, l-1, r-1));
  }
  
  // O((N+Q)log(N+Q))
  points.sort_by_key(|(_, x, _)| -(*x as i64));
  
  let mut results = vec![0; q];
  
  // O((N+Q)logN)
  let mut st = BIT::new(n+1);
  for (i, x, y) in points {
    if i == n {
      st.add(y+1, 1);
    } else {
      let ranges = st.sum(y+1) - st.sum(x);
      results[i] = y + 1 - x - ranges;
    }
  }
  
  for r in results {
    println!("{}", r);
  }
}