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 IOS ios::sync_with_stdio(false);cin.tie(0)
#define fre freopen("C:\\in.txt", "r", stdin)
#define _for(i,a,b) for(int i=a; i< b; i++)
#define _rep(i,a,b) for(int i=a; i<=b; i++)
#define lowbit(a) ((a)&-(a))
#define inf 0x3f3f3f3f
#define endl "\n"
using namespace std;
typedef long long ll;
template <class T>
void read(T &x)
{
    char c; bool op=0;
    while(c=getchar(), c<'0'||c>'9') if(c=='-') op=1;
    x=c-'0';
    while(c=getchar(), c>='0'&&c<='9') x=x*10+c-'0';
    if(op) x=-x;
}

const int maxn=5e5+5;
int T, n, m, a[maxn];
int res, num[1000005], ans[maxn];
struct Node{
    int l, r, idx;
}q[maxn];
int block;

bool cmp(Node x, Node y){
    return (x.l/block)^(y.l/block)? x.l<y.l : (((x.l/block)&1)? x.r<y.r : x.r>y.r);
}

void add(int x){
    if(!num[a[x]]) res++;
    num[a[x]]++;
}

void del(int x){
    num[a[x]]--;
    if(!num[a[x]]) res--;
}

int main()
{
    //read(T);
    T=1;
    while(T--)
    {
        read(n); read(m);
        memset(num, 0, sizeof(num));
        res=0;
        _rep(i, 1, n) read(a[i]);

        _rep(i, 1, m) read(q[i].l), read(q[i].r), q[i].idx=i;
        block=n/sqrt(m*2/3);
        sort(q+1, q+1+m, cmp);
        int l=0, r=0;
        _rep(i, 1, m){
            int ql=q[i].l, qr=q[i].r;
            while(l<ql) del(l++);
            while(l>ql) add(--l);
            while(r<qr) add(++r);
            while(r>qr) del(r--);
            ans[q[i].idx]=res;
        }
        _rep(i, 1, m) printf("%d\n", ans[i]);
    }
    return 0;
}