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)

#include <stdio.h>
#include <vector>
const int N = 500005;
int n, m;
int c[2][N], ans[N];
std::vector<int> v[N], d[N];
int a[N], lef[N], las[N], P[N];
void Insert(int t, int x, int d)
{
    for (; x; x -= x & -x)
        c[t][x] += d;
}
int Query(int t, int x)
{
    int ret = 0;
    for (; x <= n; x += x & -x)
        ret += c[t][x];
    return ret;
}
int main()
{
    int i, j, x, y;
    scanf("%d%d", &n, &m);
    for (i = 1; i <= n; i++)
    {
        scanf("%d", &a[i]);
        lef[i] = las[a[i]];
        las[a[i]] = i;
        if (i - lef[i] == lef[i] - lef[lef[i]])
            P[i] = P[lef[i]];
        else
            P[i] = lef[lef[i]];
    }
    for (i = 1; i <= m; i++)
        scanf("%d%d", &x, &y),
            v[y].push_back(x),
            d[y].push_back(i);
    for (i = 1; i <= n; i++)
    {
        if (lef[i])
            Insert(0, lef[i], -1),
                Insert(1, P[lef[i]], 1),
                Insert(1, lef[i], -1);
        Insert(0, i, 1);
        Insert(1, P[i], -1);
        Insert(1, i, 1);
        for (j = 0; j < v[i].size(); j++)
            ans[d[i][j]] = Query(0, v[i][j]) + !Query(1, v[i][j]);
    }
    for (i = 1; i <= m; i++)
        printf("%d\n", ans[i]);
}