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, non_snake_case, dead_code, non_upper_case_globals)]
use {
    proconio::{marker::*, *},
    std::{cmp::*, collections::*, mem::*},
};

#[fastout]
fn main() {
    input! {//
        n:usize,
        q:usize,
        c:[Usize1;n],
        mut lr:[(Usize1,Usize1);q],
    };
    let mut bt = SEG::<SUM>::new(n + 111);
    let mut ql = vec![vec![]; n + 5];
    let mut qid = vec![vec![]; q + 5];
    for (i, &(l, r)) in lr.iter().enumerate() {
        ql[r].push(l);
        qid[r].push(i as usize);
    }

    let mut lst = vec![!0; n + 1];
    let mut anss = vec![0; q + 1];
    for i in 0..n {
        if lst[c[i]] != !0 {
            bt.add(lst[c[i]], &(-1));
        }
        bt.add(i, &1);
        lst[c[i]] = i;
        for j in 0usize..qid[i].len() as usize {
            anss[qid[i][j]] = bt.query_range(ql[i][j]..=i);
        }
    }

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

pub trait Monoid {
    type T: Clone;
    fn id() -> Self::T;
    fn op(a: &Self::T, b: &Self::T) -> Self::T;
}
pub struct SUM {}
impl Monoid for SUM {
    type T = i64;
    fn id() -> Self::T {
        0
    }
    fn op(a: &Self::T, b: &Self::T) -> Self::T {
        *a + *b
    }
}
/// Segment Tree
pub struct SEG<M: Monoid> {
    n: usize,
    buf: Vec<M::T>,
}
impl<M: Monoid> SEG<M> {
    pub fn new(n: usize) -> SEG<M> {
        SEG {
            n,
            buf: vec![M::id(); 2 * n],
        }
    }
    pub fn update(&mut self, k: usize, a: M::T) {
        let mut k = k + self.n;
        self.buf[k] = a;
        while k > 0 {
            k >>= 1;
            self.buf[k] = M::op(&self.buf[k << 1], &self.buf[(k << 1) | 1]);
        }
    }
    pub fn add(&mut self, k: usize, a: &M::T) {
        let mut k = k + self.n;
        self.buf[k] = M::op(&self.buf[k], a);
        while k > 0 {
            k >>= 1;
            self.buf[k] = M::op(&self.buf[k << 1], &self.buf[(k << 1) | 1]);
        }
    }
    pub fn get(&self, i: usize) -> M::T {
        self.query(i, i + 1)
    }
    pub fn query_range<R: std::ops::RangeBounds<usize>>(&self, range: R) -> M::T {
        let l = match range.start_bound() {
            std::ops::Bound::Excluded(&x) => {
                assert!(x > 0);
                x - 1
            }
            std::ops::Bound::Included(&x) => x,
            std::ops::Bound::Unbounded => 0,
        };
        let r = match range.end_bound() {
            std::ops::Bound::Excluded(&x) => x,
            std::ops::Bound::Included(&x) => (x + 1),
            std::ops::Bound::Unbounded => self.n,
        };
        self.query(l, r)
    }
    pub fn query(&self, l: usize, r: usize) -> M::T {
        let mut vl = M::id();
        let mut vr = M::id();
        let mut l = l + self.n;
        let mut r = r + self.n;
        while l < r {
            if l & 1 == 1 {
                vl = M::op(&vl, &self.buf[l]);
                l += 1;
            }
            if r & 1 == 1 {
                r -= 1;
                vr = M::op(&self.buf[r], &vr);
            }
            l >>= 1;
            r >>= 1;
        }
        M::op(&vl, &vr)
    }
}