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: Runtime Error)

def main():
    N, Q = map(int, input().split())
    C = list(map(int, input().split()))
    sq = int(N ** 0.5)

    Qu = [[] for _ in range(N // sq + 1)]
    for i in range(Q):
        l, r = map(int, input().split())
        l, r = l - 1, r
        Qu[l // sq].append((r, l, i))
    ans = [0] * Q
    for qr in Qu:
        qr.sort()
        rp, lp = -1, -1
        d = [0] * N
        c = 0
        for r, l, i in qr:
            if rp == -1:
                rp, lp = l, l
            for j in range(rp, r):
                d[C[j]] += 1
                if d[C[j]] == 1:
                    c += 1
            if l < lp:
                for j in range(l, lp):
                    d[C[j]] += 1
                    if d[C[j]] == 1:
                        c += 1
            if l > lp:
                for j in range(lp, l):
                    d[C[j]] -= 1
                    if d[C[j]] == 0:
                        c -= 1
            lp, rp = l, r
            ans[i] = c
    print('\n'.join(str(i) for i in ans))

main()