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: Accepted)

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;



//1-indexedに注意！！！
struct BIT{
    private:
    int n,n_;
    vector<long long> bit;

    public:
    BIT(int n):n(n){
        bit.resize(n+1);
        n_ = 1;
        while(n_<=n) n_<<=1;
        n_ >>= 1;
    }
    //1-index
    long long sum(int i){
        long long res = 0;
        while(i > 0){
            res += bit[i];
            i -= i&-i;
        }
        return res;
    }
    //1-index
    void add(int i,long long val){
        while(i <= n){
            bit[i] += val;
            i += i&-i;
        }
    }
    //return 1-index
    int lowerbound(long long w){
        if(w <= 0) return 0;
        int x = 0;
        for(int k=n_;k>0;k>>=1){
            if(x+k<=n&&bit[x+k]<w){
                w -= bit[x+k];
                x += k;
            }
        }
        return x+1;
    }
};



int main(){
    int n;
    scanf("%d",&n);
    int q;
    scanf("%d",&q);
    vector<int> c(n);
    rep(i,n) scanf("%d",&c[i]),--c[i];
    vector<vector<P>> r(n);
    rep(i,q){
        int left,right;
        scanf("%d %d",&left,&right);
        --left;--right;
        r[right].push_back(P(left,i));
    }

    vector<int> queryans(q,0);

    vector<int> color(n,-1);
    BIT bit(n);

    rep(i,n){
        if(color[c[i]]==-1){
            bit.add(i+1,1);
            color[c[i]] = i+1;
        }
        else{
            bit.add(color[c[i]],-1);
            bit.add(i+1,1);
            color[c[i]] = i+1;
        }

        rep(j,r[i].size()){
            queryans[r[i][j].second] = bit.sum(i+1) - bit.sum(r[i][j].first);
        }
    }

    rep(i,q) printf("%d\n",queryans[i]); // cout << queryans[i] << endl;

    return 0;
}