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};

struct FenwikTree {
    size: usize,
    depth: usize,
    tree: Vec<i64>
}

impl FenwikTree {
    fn new(n: usize) -> Self {
        let size = n;
        let mut v = size;
        let mut tmp = 0;
        while v > 0 {
            tmp += 1;
            v >>= 1
        }
        let depth = tmp;
        let tree = vec![0; size + 1];

        FenwikTree {
            size, depth, tree
        }
    }

    fn _bitsum(&self, mut i: usize) -> i64 {
        let mut ret = 0;
        while i > 0 {
            ret += self.tree[i];
            i ^= i & (1 + !i);
        }
        ret
    }

    fn bitsum(&self, l:usize, r:usize) -> i64 {
        self._bitsum(r) - self._bitsum(l)
    }

    fn bitadd(&mut self, mut i:usize, x:i64) {
        i += 1;
        while i <= self.size {
            self.tree[i] += x;
            i += i & (1 + !i);
        }
    }

    fn lower_bound(&self, x:i64) -> usize {
        let mut _sum: i64 = 0;
        let mut pos: usize = 0;
        let mut v: usize = 1 << self.depth;
        for _ in (0..self.depth).rev() {
            let k = pos + v;
            if k <= self.size && _sum + self.tree[k] < x {
                _sum += self.tree[k];
                pos = k;
            }
            v >>= 1;
        }
        pos + 1
    }
}

#[fastout]
fn main() {
    input!{
        n: usize, q:usize,
        c: [Usize1; n],
        query: [(usize, usize); q]
    }
    let mut last = vec![n; n];
    let mut g = query.iter().enumerate().collect::<Vec<_>>();
    g.sort_by_cached_key(|(_, &(_, z))| z);
    let mut idx = 0;
    let mut ans = vec![0; q];
    let mut bit = FenwikTree::new(n);
    for &(i, &(l, r)) in &g {
        // println!("{} {} {}", i, l, r);
        while idx < r {
            if last[c[idx]] < n {
                bit.bitadd(last[c[idx]], -1);
            }
            last[c[idx]] = idx;
            bit.bitadd(idx, 1);
            idx += 1;
        }
        ans[i] = bit.bitsum(l-1, r);
    }
    println!("{}", ans.iter().map(|x| x.to_string()).collect::<Vec<_>>().join("\n"));
}