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: Time Limit Exceeded)

use proconio::{input, fastout};
use std::collections::HashMap;

#[fastout]
fn main() {
    input! {
        n: usize,q: usize,
        c: [i32; n],
    }
    let mut a: Vec<HashMap<i32,i32>> = vec![HashMap::new()];
    for i in 0..n {
        if i == 0 {
            a[0].insert(c[0], 1);
        }
        else {
            a.push(a[i-1].clone());
            let p = a[i].entry(c[i]).or_insert(0);
            *p += 1;
        }
    }
    for _ in 0..q {
        input! {
            l: usize,r: usize,
        }
        let mut ans = 0;
        for (k, v) in a[r-1].iter() {
            if l == 1 || v - match a[l-2].get(k) {
                None => 0,
                Some(&i) => i,
            } > 0 {
                ans += 1
            }
        }
        println!("{}", ans);
    }
}