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)

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define ALL(x) x.begin(), x.end()
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
random_device rnd;
mt19937 mt(rnd());
using ll = long long;
using lld = long double;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using PII = pair<int, int>;
const int IINF = 1 << 30;
const ll INF = 1ll << 60;
const ll MOD = 1000000007;

int main()
{
    int n, q;
    cin >> n >> q;
    vector<int> tmp;
    rep(i, n)
    {
        int t;
        cin >> t;
        tmp.push_back(t);
    }

    vector<int> col(n + 1, 0);
    col[tmp[0]]++;
    int num = 1;
    int cl = 0, cr = 0;
    vector<pair<pair<int, int>, int>> query(q);
    rep(i, q)
    {
        int l, r;
        cin >> l >> r;
        l--;
        r--;
        query[i] = {{-l, -r}, i};
    }
    sort(ALL(query));
    VI ans(q, 0);
    rep(i, q)
    {
        int l = -query[i].first.first;
        int r = -query[i].first.second;

        if (r < cr)
        {
            while (r != cr)
            {
                col[tmp[cr]]--;
                if (col[tmp[cr]] == 0)
                    num--;
                cr--;
            }
        }
        if (r > cr)
        {
            while (r != cr)
            {

                cr++;
                if (col[tmp[cr]] == 0)
                    num++;
                col[tmp[cr]]++;
            }
        }

        if (l > cl)
        {
            while (l != cl)
            {
                col[tmp[cl]]--;
                if (col[tmp[cl]] == 0)
                    num--;
                cl++;
            }
        }

        if (l < cl)
        {
            while (l != cl)
            {
                cl--;
                if (col[tmp[cl]] == 0)
                    num++;
                col[tmp[cl]]++;
            }
        }
        ans[query[i].second] = num;
    }
    rep(i, q)
    {
        cout << ans[i] << "\n";
    }
    return 0;
}