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 PyPy3 (7.3.0) (judge verdict: Time Limit Exceeded)

import sys
input = sys.stdin.readline

class BIT:

    def __init__(self, N):
        self.N = N
        self.bit = [0] * (N+1)

    def add(self, x, a):
        while x <= self.N:
            self.bit[x] += a
            x += x & -x

    def sum(self, x):
        ret = 0
        while x != 0:
            ret += self.bit[x]
            x -= x & -x
        return ret

N, Q = map(int, input().split())
c = list(map(int, input().split()))
rl = [None] * Q
for i in range(Q):
    l, r = map(int, input().split())
    rl[i] = (r, l, i)
rl.sort()
bit = BIT(N+1)
ans = [None] * Q
last_idx = [-1] * (N+1)
j = 0
for r, l, i in rl:
    while j < r:
        if last_idx[c[j]] == -1:
            last_idx[c[j]] = j
        else:
            bit.add(last_idx[c[j]]+1, -1)
            last_idx[c[j]] = j
        bit.add(j+1, 1)
        j += 1
    ans[i] = bit.sum(r) - bit.sum(l-1)
for a in ans:
    print(a)