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 C++ (GCC 9.2.1) (judge verdict: Time Limit Exceeded)

#include <bits/stdc++.h>

using namespace std;
const int MN=5e5+10;
int t[MN], R=1, n;
set<int>tree[3*MN];

set<int> query(int cur, int beg, int en, int x, int y){
    set<int> sum;
    if(beg>=x&&en<=y) return tree[cur];
    int sr=(beg+en)/2;
    if(sr>=x){
        auto p=query(2*cur, beg, sr, x, y);
        sum.insert(p.begin(), p.end());
    }
     if(sr<y){
        auto p=query(2*cur+1, sr+1, en, x, y);
        sum.insert(p.begin(), p.end());
    }
    return sum;
}
int main()
{
    ios_base::sync_with_stdio(0);
    int q;
    cin>>n>>q;
    while(n>R) R*=2;
    for(int i=1; i<=n; ++i){
        cin>>t[i];
        tree[R+i-1].insert(t[i]);
    }
    for(int i=R-1; i>=1; --i){
        tree[i].insert(tree[2*i].begin(), tree[2*i].end());
        tree[i].insert(tree[2*i+1].begin(), tree[2*i+1].end());
    }
    while(q--){
        int a, b;
        cin>>a>>b;
        cout<<(int)query(1, 1, R, a, b).size()<<'\n';
    }
    return 0;
}