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)

struct Mo {
    len: usize,
    left: Vec<usize>, right: Vec<usize>,
    k: usize,
    v: Vec<usize>, cnt: Vec<usize>,
}

impl Mo {
    fn new(n: usize, v: Vec<usize>) -> Mo {
        Mo {
            len: (n as f32).sqrt() as usize,
            left: Vec::new(), right: Vec::new(),
            k: 0,
            v, cnt: vec![0; n],
        }
    }

    fn push(&mut self, l: usize, r: usize) {
        self.left.push(l);
        self.right.push(r);
    }

    fn solve(&mut self) -> Vec<usize> {
        let mut order: Vec<usize> = (0..self.left.len()).collect();
        order.sort_by(|&i, &j| {
            if self.left[i] / self.len != self.left[j] / self.len {
                self.left[i].cmp(&self.left[j])
            } else {
                self.right[i].cmp(&self.right[j])
            }
        });

        let mut res = vec![0; self.left.len()];
        let (mut nl, mut nr) = (0, 0);
        for i in order {
            while nl > self.left[i] {
                nl -= 1;
                self.add(nl);
            }
            while nr < self.right[i] {
                self.add(nr);
                nr += 1;
            }
            while nl < self.left[i] {
                self.del(nl);
                nl += 1;
            }
            while nr > self.right[i] {
                nr -= 1;
                self.del(nr);
            }
            res[i] = self.k;
        }
        res
    }

    fn add(&mut self, i: usize) {
        let x = self.v[i];
        if self.cnt[x] == 0 { self.k += 1; }
        self.cnt[x] += 1;
    }

    fn del(&mut self, i: usize) {
        let x = self.v[i];
        self.cnt[x] -= 1;
        if self.cnt[x] == 0 { self.k -= 1; }
    }
}

fn main() {
    let (n, q): (usize, usize) = {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        let mut iter = buf.split_whitespace();
        (
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
        )
    };
    
    let c: Vec<usize> = {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        let iter = buf.split_whitespace();
        iter.map(|x| x.parse().unwrap()).collect()
    };

    let mut mo = Mo::new(n, c);
    for _ in 0..q {
        let (l, r): (usize, usize) = {
            let mut buf = String::new();
            std::io::stdin().read_line(&mut buf).unwrap();
            let mut iter = buf.split_whitespace();
            (
                iter.next().unwrap().parse::<usize>().unwrap() - 1,
                iter.next().unwrap().parse().unwrap(),
            )
        };
        mo.push(l, r);
    }
    
    let ans = mo.solve();
    for i in 0..q {
        println!("{}", ans[i]);
    }
}