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: Accepted)

N,Q = gets.split.map &:to_i
C = gets.split.map &:to_i

q = Q.times.map do |i| 
    l,r = gets.split.map(&:to_i)
    [l-1,r-1,i]
end
    
q.sort_by!{|l,r,i| r}

$BIT = [0]*(N+1)

def add(x)
    while x<=N
        $BIT[x] += 1
        x += x & -x
    end
end

def sum(x)
    s = 0
    while x>0
        s += $BIT[x]
        x -= x & -x
    end
    s
end

ans = [-1]*Q
csr = 0
last = [nil]*N
q.each do |l,r,idx|
    while csr<=r
        c = C[csr]
        add(last[c]+1) if last[c]

        last[c] = csr
        csr += 1
    end

    ans[idx] = (r-l+1) - (sum(r+1) - sum(l))
end

puts ans