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)

#pragma region RegionDefs
#include <bits/stdc++.h>
#define rep(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define reps(i,l,r) for(int i=(l),i##_len=(r);i<i##_len;++i)
#define repr(i,l,r) for(int i=(r)-1,i##_left=(l);i>=i##_left;--i)
#define all(x) begin(x),end(x)
using namespace std;
typedef long long ll;
const ll INF = 1e9;
template<class T=ll> using V = vector<T>;
template<class T=ll> using PQ = priority_queue<T>;
template<class T=ll> using PQG = priority_queue<T, V<T>, greater<T>>;
const ll MOD = 1000000007LL;
void in() {}
template<class Head, class... Tail>
void in(Head&& head, Tail&&... tail) { cin >> head; in(move(tail)...); }
#define IN(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define INS(T, ...) T __VA_ARGS__; in(__VA_ARGS__)
#define VIN(T, v, n) V<T> v(n); for(auto& _elem:v)cin>>_elem
template<class T>bool chmax(T &a, const T &b) {if (a<b) {a=b; return 1;} return 0;}
template<class T>bool chmin(T &a, const T &b) {if (a>b) {a=b; return 1;} return 0;}
template<class T>
string join(vector<T>& v, string delim="") { ostringstream os; rep(i,v.size())i?os<<delim<<v[i]:os<<v[0]; return os.str(); }
#pragma endregion RegionDefs

struct BIT {
    ll n;
    vector<ll> bit;
    BIT(ll n):n(n),bit(n+1,0) {}

    void add(ll i, ll x){
        if(i==0) return;
        for(ll k =i ; k <= n; k += (k & -k)){
            bit[k]+=x;
        }
    }

    ll sum(ll i) {
        if (i < 0) return 0;
        ll s = 0;
        for (int k = i; k > 0; k -= (k & -k)) {
            s += bit[k];
        }
        return s;
    }

    ll sum2(ll l, ll r) {
        return sum(r)-sum(l-1);
    }
};

void solve()
{
    IN(n, q);
    VIN(ll, c, n);
    V<pair<ll,pair<ll,ll>>> v;
    rep(i, q) {
        IN(l, r);
        v.emplace_back(r, make_pair(l-1,i));
    }
    sort(all(v));
    ll last[n] = {};
    int j = 0;
    BIT bit(n);
    ll res[q];
    rep(i, q) {
        for(int k = j; k < v[i].first; ++k) {
            ll l = last[c[k]];
            last[c[k]] = k;
            bit.add(l, -1);
            bit.add(last[c[k]], 1);
        }
        j = v[i].first;
        res[v[i].second.second] = bit.sum2(v[i].second.first, v[i].first);
    }
    rep(i, q) {
        cout << res[i] << endl;
    }
}

int main()
{
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(numeric_limits<double>::max_digits10);

    solve();

    return 0;
}