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 Python (3.8.2) (judge verdict: Accepted)

import sys
import numpy as np
import numba
from numba import njit
from numba.types import Omitted
i4 = numba.int32
i8 = numba.int64

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

Bsize = 700

@njit((i8[:, :], ), cache=True)
def Mo_argsort(LR):
    L = LR[:, 0]
    R = LR[:, 1]
    key1 = L // Bsize
    key2 = np.where(key1 & 1, -R, R)
    key = (key1 << 32) + key2
    return np.argsort(key)

@njit((i8[:], i8[:, :]), cache=True)
def main(A, LR):
    N = len(A)
    Q = len(LR)
    ind = Mo_argsort(LR)
    count = np.zeros(N + 1, np.int64)
    ans = 0
    

    def add(x):
        nonlocal ans
        if not count[x]:
            ans += 1
        count[x] += 1

    def rem(x):
        nonlocal ans
        count[x] -= 1
        if not count[x]:
            ans -= 1

    answers = np.empty(Q, np.int64)
    nl, nr = 0, 0
    for i in ind:
        l, r = LR[i]
        l -= 1
        # 区間 [l, r) に対する計算
        while nl > l:
            nl -= 1
            add(A[nl])
        while nr < r:
            add(A[nr])
            nr += 1
        while nl < l:
            rem(A[nl])
            nl += 1
        while nr > r:
            nr -= 1
            rem(A[nr])
        #  答を求めて ans[i] に格納する
        answers[i] = ans
    return answers

N, Q = map(int, readline().split())
A = np.array(readline().split(), np.int64)
LR = np.array(read().split(), np.int64).reshape(Q,2)

ans = main(A, LR)
print('\n'.join(map(str, ans.tolist())))