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 Go (1.14.1) (judge verdict: Accepted)

package main

import (
	"bufio"
	. "fmt"
	"io"
	"os"
	"sort"
)

// github.com/EndlessCheng/codeforces-go
func run(_r io.Reader, _w io.Writer) {
	out := bufio.NewWriter(_w)
	defer out.Flush()
	buf := make([]byte, 4096)
	_i := len(buf)
	rc := func() byte {
		if _i == len(buf) {
			_r.Read(buf)
			_i = 0
		}
		b := buf[_i]
		_i++
		return b
	}
	r := func() (x int) {
		b := rc()
		for ; '0' > b; b = rc() {
		}
		for ; '0' <= b; b = rc() {
			x = x*10 + int(b&15)
		}
		return
	}
	type pair struct{ l, r, i int }

	n, q := r(), r()
	a := make([]int, n+1)
	for i := 1; i <= n; i++ {
		a[i] = r()
	}
	qs := make([]pair, q)
	for i := range qs {
		qs[i] = pair{r(), r(), i}
	}
	sort.Slice(qs, func(i, j int) bool { return qs[i].r < qs[j].r })

	tree := make([]int, n+1)
	add := func(i int, val int) {
		for ; i <= n; i += i & -i {
			tree[i] += val
		}
	}
	query := func(l, r int) (s int) {
		for ; r > l; r &= r - 1 {
			s += tree[r]
		}
		for ; l > r; l &= l - 1 {
			s -= tree[l]
		}
		return
	}

	ans := make([]int, q)
	posR := make([]int, n+1)
	i := 1
	for _, q := range qs {
		for ; i <= q.r; i++ {
			if p := posR[a[i]]; p > 0 {
				add(p, -1)
			}
			add(i, 1)
			posR[a[i]] = i
		}
		i = q.r + 1
		ans[q.i] = query(q.l-1, q.r)
	}
	for _, v := range ans {
		Fprintln(out, v)
	}
}

func main() { run(os.Stdin, os.Stdout) }