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 Ruby (2.7.1) (judge verdict: Time Limit Exceeded)

N, Q = gets.split.map(&:to_i)
Cs = [nil] + gets.split.map(&:to_i)
LRs = Q.times.map{gets.split.map(&:to_i)}

class BIT
  def initialize(n)
    @n, @b = n, Array.new(n + 1, 0)
  end

  def querry(i)
    r = 0
    while i > 0
      r += @b[i]
      i -= i & -i
    end
    r
  end

  def add(i, v)
    while i <= @n
      @b[i] += v
      i += i & -i
    end
  end
end

s, ans, m, b = 0, [], [], BIT.new(N)
LRs.map.with_index.sort_by{|(l, r), i| r}.each do |(l, r), i|
  (s + 1 .. r).each do |j|
    c = Cs[j]
    k = m[c]
    m[c] = j
    b.add(j, 1)
    b.add(k, -1) if k
  end
  ans[i] = b.querry(r) - b.querry(l - 1)
  s = r
end
puts ans