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::marker::Usize1;
fn main() {
    proconio::input! {
        n: usize,
        q: usize,
        c: [Usize1;n],
        lr: [(Usize1,usize);q],
    }
    let mut k: Vec<_>=(0..q).collect();
    k.sort_unstable_by_key(|k|lr[*k].1);
    let mut a=vec![0;q];
    let mut rm=0;
    let mut t=vec![0;n+1];
    let mut p=vec![n;n];
    for k in k {
        let (l,r)=lr[k];
        while rm<r {
            let c=c[rm];
            if p[c]<n {
                let mut i=p[c]+1;
                while i<=n {
                    t[i]-=1;
                    i+=i&i.wrapping_neg();
                }
            }
            p[c]=rm;
            let mut i=rm+1;
            while i<=n {
                t[i]+=1;
                i+=i&i.wrapping_neg();
            }
            rm+=1;
        }
        let mut s=0;
        let mut i=r;
        while i>0 {
            s+=t[i];
            i-=i&i.wrapping_neg();
        }
        let mut i=l;
        while i>0 {
            s-=t[i];
            i-=i&i.wrapping_neg();
        }
        a[k]=s;
    }
    for a in a {
        println!("{}",a);
    }
}