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(unused_imports)]
use {
   proconio::{fastout, input, marker::*},
   std::cmp::*,
   std::collections::*,
};

#[fastout]
fn main() {
   input! {
      n: usize,
      q: usize,
      c: [Usize1; n],
      mut lr: [(Usize1, Usize1); q]
   }
   let mut query = vec![];
   for (i, (l, r)) in lr.iter().enumerate() {
      query.push((*l, *r, i));
   }

   let mut ans = vec![0; q];

   query.sort_by_key(|(_, r, _)| *r);
   let mut append = vec![n; n];
   let mut bit = vec![0; n + 1];

   let mut rn = !0;
   for &(l, r, i) in query.iter() {
      for j in rn + 1..=r {
         if append[c[j]] != n {
            bit.add(append[c[j]], !0);
         }
         append[c[j]] = j;
         bit.add(append[c[j]], 1);
      }
      rn = r;
      ans[i] = bit.range(l, r + 1);
   }
   for a in ans {
      println!("{}", a);
   }
}

use std::ops::{AddAssign, Sub};
trait BIT<T: Copy + Clone + Sub + AddAssign> {
   fn add(&mut self, idx: usize, w: T);
   fn sum(&self, idx: usize) -> T;
   fn range(&self, l: usize, r: usize) -> T;
}

impl<T: Copy + Clone + Sub<Output = T> + AddAssign> BIT<T> for [T] {
   /// Example:
   /// ```
   /// let mut bit = vec![0; n+1];
   /// let q = vec![(0,2), (1,3), (3,1)];
   /// for &(i, w) in q.iter() {
   ///    bit.add(i, w);
   /// }
   /// assert_eq!(bit.sum(1), 5);
   /// assert_eq!(bit.range(1, 3), 3);
   /// assert_eq!(bit.range(1, 4), 4);
   /// ```
   fn add(&mut self, idx: usize, w: T) {
      let mut j = (idx + 1) as i64;
      while j < self.len() as i64 {
         self[j as usize] += w;
         j += j & -j;
      }
   }
   /// [0, r]
   fn sum(&self, idx: usize) -> T {
      let mut i = (idx + 1) as i64;
      let mut sum = self[0];
      while i != 0 {
         sum += self[i as usize];
         i -= i & -i;
      }
      sum
   }
   /// [l, r)
   fn range(&self, l: usize, r: usize) -> T {
      match (l, r) {
         (0, _) => self.sum(r - 1),
         _ => self.sum(r - 1) - self.sum(l - 1),
      }
   }
}