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: Runtime Error)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

#define SZ(x) (int)((x).size())
#define xx first
#define yy second
#define pii pair<int, int>

#define dbg if (0)

const int N = 1e5 + 1;

int n, q;
int c[N], l[N], r[N];
int frq[N];

void solve() {
    cin >> n >> q;
    for (int i = 0; i < n; i++)
        cin >> c[i];

    dbg cerr << "23\n";

    vector<pair<pii, int>> rng;
    for (int i = 0; i < q; i++) {
        cin >> l[i] >> r[i];
        --l[i], --r[i];
        rng.push_back({{l[i], r[i]}, i});
    }
    sort(rng.begin(), rng.end()); 

    dbg cerr << "32\n";

    int lp = 0, rp = -1;
    vector<int> ans(q);

    int on = 0;
    fill(frq, frq + N, 0);
    for (int i = 0; i < q; i++) {
        auto cur = rng[i];
        int idx = cur.yy;
        int lb = cur.xx.xx, rb = cur.xx.yy;
        while (lp > lb) {
            --lp;
            if (!frq[c[lp]])
                on++;
            frq[c[lp]]++;
        }
        while (rp < rb) {
            ++rp;
            if (!frq[c[rp]])
                on++;
            frq[c[rp]]++;
        }
        while (lp < lb) {
            frq[c[lp]]--;
            if (!frq[c[lp]])
                on--;
            ++lp;
        }
        while (rp > rb) {
            frq[c[rp]]--;
            if (!frq[c[rp]])
                on--;
            --rp;
        }
        ans[idx] = on;
    }

    dbg cerr << "70\n";

    for (int i = 0; i < q; i++)
        cout << ans[i] << '\n';
}
int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    // int _; cin >> _; while (_--)
    solve();
    return 0;
}