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: Accepted)

def solve():
    import sys
    input = sys.stdin.readline

    class FenwickTree:
        def __init__(self, size):
            self.size = size
            self.array = [0]*size
    
        def add(self, index, value):
            while index < self.size:
                self.array[index] += value
                index += index&(-index)
    
        def sum(self, index):
            answer = 0
            while index > 0:
                answer += self.array[index]
                index -= index&(-index)
            return answer
    
        def rangesum(self, start, end):
            return self.sum(end)-self.sum(start-1)


    N, Q = map(int, input().split())
    *c, = map(int, input().split())
    tree2 = FenwickTree(N+1)
    m = [tuple(map(int, input().split())) for _ in range(Q)]
    idxs = sorted(tuple(range(Q)), key=lambda i: m[i][1])

    right = 0
    pos = [-1] * (N+1)
    ans = [-1] * (Q)

    for idx in idxs:
        l, r = m[idx]
        for i in range(right, r):
            x = pos[c[i]]
            if x != -1:
                tree2.add(x, -1)
            pos[c[i]] = i+1
            tree2.add(i+1, 1)
        ans[idx] = tree2.rangesum(l, r)
        right = r
    for i in ans:
        print(i)


solve()