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)

mod BIT {
    use std::clone::Clone;
    use std::convert::From;
    use std::ops::{Add, AddAssign, Sub};

    #[derive(Clone, Debug)]
    pub struct BIT<T> {
        array: Vec<T>,
    }

    impl<T> BIT<T>
    where
        T: Add + Sub + Clone + Copy + From<u8> + AddAssign,
    {
        pub fn new(size: usize) -> BIT<T> {
            let v: Vec<T> = vec![T::from(0u8); size + 1];
            Self { array: v }
        }
        pub fn add(&mut self, mut i: usize, x: T) {
            let n = self.array.len();
            while i <= n {
                self.array[i] += x;
                i += i & i.wrapping_neg();
            }
        }
    }

    pub trait Sum<T, U> {
        fn sum(&self, i: T) -> U;
    }

    impl<T> Sum<usize, T> for BIT<T>
    where
        T: Add + Sub + Clone + Copy + From<u8> + AddAssign,
    {
        fn sum(&self, mut i: usize) -> T {
            if i == 0 {
                return T::from(0u8);
            }
            let mut s = T::from(0u8);

            while i > 0 {
                s += self.array[i];
                i -= i & i.wrapping_neg();
            }
            s
        }
    }

    impl<T> Sum<(usize, usize), T> for BIT<T>
    where
        T: Add + Sub + Clone + Copy + From<u8> + AddAssign,
        T: std::ops::Sub<Output = T>,
    {
        fn sum(&self, i: (usize, usize)) -> T {
            let sum_l = <BIT<T> as Sum<usize, T>>::sum(self, i.0 - 1);
            let sum_r = <BIT<T> as Sum<usize, T>>::sum(self, i.1);
            sum_r - sum_l
        }
    }

    #[test]
    fn test_sum() {
        let mut a = BIT::new(100);

        for i in 1..101 {
            a.add(i, i);
        }

        assert_eq!((0..101).sum::<usize>(), a.sum(100));
        assert_eq!((2..101).sum::<usize>(), a.sum((2, 100)));
    }
}

use proconio::{fastout, input, marker::*};
use BIT::Sum;

#[fastout]
fn main() {
    input!(n: usize, q: usize, c: [usize; n], lr: [[Usize1; 2]; q]);

    let mut c_vv = vec![vec![0usize; 0]; n];
    let mut c_v = vec![-1i64; n + 1];
    for (i, v) in c.iter().enumerate() {
        let l = c_v[*v];
        if l != -1 {
            c_vv[l as usize].push(i);
        }
        c_v[*v] = i as i64;
    }

    let mut lr_vec = vec![vec![vec![0usize; 2]; 0]; n];
    for (i, v) in lr.iter().enumerate() {
        lr_vec[v[0]].push(vec![v[1], i]);
    }

    let mut ans = vec![0usize; q];
    let mut bi_tree = BIT::BIT::<usize>::new(n);
    for i in (0..n).rev() {
        for cv in &c_vv[i] {
            bi_tree.add(*cv + 1, 1);
        }

        for v in &lr_vec[i] {
            ans[v[1]] = (v[0] - i + 1) - bi_tree.sum(v[0] + 1);
        }
    }
    for v in &ans {
        println!("{}", *v);
    }
}