Dequeue in java

import java.util.*;

public class test {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        Deque<Integer> deque = new ArrayDeque<>();
        HashSet<Integer> set = new HashSet<>();
       
        int n = in.nextInt();
        int m = in.nextInt();
        int max = Integer.MIN_VALUE;

        for (int i = 0; i < n; i++) {
            int input = in.nextInt();
           
            deque.add(input);
            set.add(input);
           
            if (deque.size() == m) {
                if (set.size() > max) max = set.size();
                int first = deque.remove();
                if (!deque.contains(first)) set.remove(first);
            }
        }
       
        System.out.println(max);
    }
}

Sample Input

6 3
5 3 5 2 3 2

Sample Output

3