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)

#[allow(unused_imports)]
use proconio::{
    fastout, input,
    marker::{Bytes, Chars, Isize1, Usize1},
};

use std::collections::BTreeSet;

#[fastout]
fn main() {
    input! {
       n:usize,
       q:usize,
       c:[usize;n]
    }
    let bs = 700;
    let mut block = vec![BTreeSet::new(); n / bs + 10];
    for (i, &x) in c.iter().enumerate() {
        block[i / bs].insert(x);
    }
    for _ in 0..q {
        input! {
            l:Usize1,r:Usize1
        }
        let mut s = BTreeSet::new();
        let mut p = l;
        while p <= r {
            if p % bs == 0 && p + bs <= r {
                s = &s | &block[p / bs];
                p += bs;
            } else {
                s.insert(c[p]);
                p += 1;
            }
        }
        println!("{}", s.len());
    }
}