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)

use proconio::input;
use proconio::marker::{Usize1};

#[allow(dead_code)]
fn type_of<T>(_: T) -> &'static str {
    std::any::type_name::<T>()
}

trait Monoid {
    fn unit() -> Self;
    fn func(self, e: Self) -> Self;
}

struct SegmentTree<T>{
    size: usize,
    data: Vec<T>,
}

impl<T> SegmentTree<T>
where T: std::fmt::Debug
{
    #[allow(dead_code)]
    pub fn dump(&self) -> () {
        eprintln!("{:?}", self.data);
    }
}

impl<T> SegmentTree<T>
where T: Monoid + Clone
{
    pub fn new(size: usize) -> Self {
        SegmentTree{
            size,
            data: vec![T::unit(); 2*size],
        }
    }
}

impl<T> SegmentTree<T>
where T: Monoid + Copy
{
    pub fn update(&mut self, idx: usize, e: T) {
        let mut idx = idx + self.size;
        while idx > 0 {
            self.data[idx] = self.data[idx].func(e);
            idx >>= 1;
        }
    }

    pub fn query(&self, l: usize, r: usize) -> Result<T, &'static str> {
        if r <= l { Err("l < r") }
        else {
            let mut ret = T::unit();
            let mut l = l + self.size;
            let mut r = r + self.size;
            while l < r {
                if l & 1 == 1 { ret = self.data[l].func(ret); l += 1;}
                if r & 1 == 1 { ret = ret.func(self.data[r-1]); r -= 1;}
                l >>= 1;
                r >>= 1;
            }
            Ok(ret)
        }
    }
}

impl Monoid for isize {
    fn unit() -> Self {
        0isize
    }

    fn func(self, e: Self) -> Self {
        self + e
    }
}

fn main() {
    input!{
        n: usize,
        q: usize,
        c: [Usize1; n],
        d: [(Usize1, Usize1); q],
    }

    let mut st = SegmentTree::<isize>::new(n);
    let mut mr = vec![None; n];
    let mut d = d.iter().enumerate().collect::<Vec<_>>();    
    d.sort_by(|&(_, (_, r)), &(_, (_, ro))| r.cmp(&ro));
    let mut mridx = 0usize;
    let mut ans = vec![0isize; q];
    for (idx, &(l, r)) in d {
        while mridx <= r {
            let nc = c[mridx];
            if let Some(pidx) = mr[nc] {
                st.update(pidx, -1);
            }
            mr[nc] = Some(mridx);
            st.update(mridx, 1);
            mridx += 1;
        }
        //eprintln!("case {}: [l, r) = [{}, {})", idx, l, r+1);
        //st.dump();
        ans[idx] = st.query(l, r+1).unwrap();
        //eprintln!("ans: {}", ans[idx]);
    }
    for i in ans {
        println!("{}", i);
    }

}