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_imports)]
#![allow(non_snake_case)]
#![allow(dead_code)]
use proconio::{input, fastout};
use proconio::marker::{Chars, Bytes, Usize1};

#[fastout]
fn main() {
    input!{
        n: usize, q:usize,
        c: [Usize1; n],
        query: [(Usize1, usize); q]
    }
    fn f(x: usize, y:usize) -> usize {
        let mut ret = x / 700 * 600000;
        if x / 700 % 2 > 0 {
            ret += 600000 - y;
        } else {
            ret += y;
        }
        ret
    }
    let mut g = query.iter().enumerate().collect::<Vec<_>>();
    g.sort_by_cached_key(|(_, &(x, y))| f(x, y));
    let mut idxl = 0;
    let mut idxr = 0;
    let mut ans = vec![0; q];
    let mut cur = vec![0; n];
    let mut scr = 0;
    for &(i, &(l, r)) in &g {
        while idxr < r {
            if cur[c[idxr]] == 0 {
                scr += 1;
            }
            cur[c[idxr]] += 1;
            idxr += 1;
        }
        while idxl > l {
            idxl -= 1;
            if cur[c[idxl]] == 0 {
                scr += 1;
            }
            cur[c[idxl]] += 1;
        }
        while idxr > r {
            idxr -= 1;
            if cur[c[idxr]] == 1 {
                scr -= 1;
            }
            cur[c[idxr]] -= 1;
        }
        while idxl < l {
            if cur[c[idxl]] == 1 {
                scr -= 1;
            }
            cur[c[idxl]] -= 1;
            idxl += 1;
        }
        ans[i] = scr;
    }
    println!("{}", ans.iter().map(|x| x.to_string()).collect::<Vec<_>>().join("\n"));
}