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: Runtime Error)

#![allow(
  non_snake_case,
  unused_variables,
  unused_assignments,
  unused_mut,
  unused_imports,
  dead_code
)]
//use proconio::fastout;
use proconio::input;
use proconio::marker::*;
use std::cmp::*;
use std::collections::*;
//use std::collections::VecDeque;

fn main() {
  input! {
     N:usize,Q:usize,
     c:[usize;N],
     lr:[(Usize1,Usize1);Q]
  }
  // 各色の最初の位置と最後の位置を記録する。
  //  let mut sta = HashMap::new();
  let mut ans = vec![0i64; N];
  let mut last = vec![-1; N];
  let mut next = vec![vec![]; N];
  for i in 0..N {
    let v = last[c[i]];
    if v != -1 {
      next[v as usize].push(i);
    }
    last[c[i]] = i as i64;
  }
  let mut qs = vec![Vec::with_capacity(N); N];
  for (qi, &(l, r)) in lr.iter().enumerate() {
    qs[l].push((r, qi));
  }
  //println!("p{:?}", prev);
  let mut bit = BIT::new(N);
  for x in (0..N).rev() {
    for &y in next[x].iter() {
      bit.add(y, 1);
    }
    //println!("prev={:?}", next);
    for &(r, qi) in qs[x].iter() {
      //println!("sum={}", bit.sum(r));
      ans[qi] = (r - x + 1) as i64 - bit.sum(r);
    }
  }

  for i in 0..Q {
    println!("{}", ans[i]);
  }
}

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;
    while i <= self.n {
      self.d[i] += x;
      i += (i as i64 & -(i as i64)) as usize;
    }
  }
  fn sum(&self, index: usize) -> T {
    let mut x = T::from_i64(0).unwrap();
    let mut i = index + 1;
    while i > 0 {
      x += self.d[i];
      i -= (i as i64 & -(i as i64)) as usize;
    }
    x
  }
  fn sum2(&self, index1: usize, index2: usize) -> T {
    self.sum(index2) - self.sum(index1)
  }
}