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: Wrong Answer)

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0; i<n; i++)
#define PI 3.14159265359
#define INF 1000100100
#define MOD 1000000007
#define all(x) (x).begin(),(x).end()
typedef long long ll;
#define P pair<ll, ll>
#define PP pair<P,int>
#define T tuple<int,int,int> 
using namespace std;

int main(){
    int n,q; cin >> n >> q;
    vector<int> data(n);
    rep(i,n) cin >> data[i];
    vector<int> left(n+1),right(n+1);
    left[0]=0;
    right[n]=0;
    map<int,int> num;
    int kind=0;
    rep(i,n){
        if(num[data[i]]==0){
            left[i+1]=left[i]+1;
            kind++;
        }
        else left[i+1]=left[i];
        num[data[i]]++;
    }
    map<int,int> num2;
    rep(i,n){
        if(num2[data[n-1-i]]==0) right[n-i-1]=right[n-i]+1;
        else right[n-i-1]=right[n-i];
        num2[data[n-1-i]]++;
    }

    rep(i,q){
        int l,r; cin >> l >> r;
        cout << left[r]+right[l-1]-kind << endl;
    }
return 0;
}