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 JavaScript (Node.js 12.16.1) (judge verdict: Time Limit Exceeded)

const main = (input) => {
  input = input.trim().split('\n').map(v => v.split(' ').map(Number))
  // const [n, q] = input[0].split(' ').map(Number)
  const stones = input[1]
  const [, , ...q] = input

  const ans = {}
  const sq = q.slice(0).sort((a, b) => a[0] === b[0] ? a[1] - b[1] : a[0] - b[0])

  while (sq.length) {

    const [start, end] = sq.shift()

    const s = new Set(stones.slice(start-1, end))
    ans[`${start}-${end}`] = s.size

    while (sq[0] && sq[0][0] === start) {
      const [_start, _end] = sq.shift()
      for (let i = end; i < _end; i++) s.add(stones[i])
      ans[`${_start}-${_end}`] = s.size
    }
  }

  for (let [s, e] of q) console.log(ans[`${s}-${e}`])
}

process.env.MYTEST ? test() : main(require('fs').readFileSync('/dev/stdin', 'utf8'))