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)

function Main(input) {
  input = input.split("\n");
  const nq = input.shift().split(" ");
  const n = parseInt(nq[0], 10);
  const q = parseInt(nq[1], 10);
  const cs = input.shift().split(" ");

  // Preload queries
  const qs = [];
  for (let qi=0; qi<q; qi++) {
    const [l, r] = input[qi].split(" ");
    qs[l-1] = qs[l-1] || [];
    qs[l-1].push([r-1, qi]);
  }

  // store the information whether the number is already appeared
  const ps = [];
  const pi = {};
  for (let i=0; i<n; i++) {
    const l = pi[cs[i]];
    if (l !== undefined) {
      ps[l] = ps[l] || [];
      ps[l].push(i);
    }
    pi[cs[i]] = i;
  }

  const ans = [];

  // Create BIT
  const d = [];
  for (let x=n-1; x>=0; --x) {
    const psLength = ps[x] && ps[x].length || 0;
    for (let y=0; y<psLength; y++) {
      let di = ps[x][y] + 1;
      for (; di<=n; di+=di&-di) {
        d[di] = d[di] || 0;
        d[di] += 1;
      }
    }
    const qsLength = qs[x] && qs[x].length || 0;
    for (let y=0; y<qsLength; y++) {
      const [r, i] = qs[x][y];
      let sum = 0;
      let ri = r + 1;
      for (; ri; ri -= ri&-ri) {
        sum += d[ri] || 0;
      }
      ans[i] = (r-x+1) - sum;
    }
  }

  console.log(ans.join("\n"));
  return;
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));