my solution: import java.util.*; public class test { public static void main(String[] args) { Scanner in = new Scanner(System.in); Deque deque = new ArrayDeque<>(); Set set = new HashSet<>(); int n = in.nextInt(); int m = in.nextInt(); int max = 0;

        for (int i = 0; i < n; i++) {
            int num = in.nextInt();
            deque.addLast(num);
            set.add(num);

        if(deque.size() == m){
            max = Math.max(max, set.size());
            int first = deque.removeFirst();
            if(!deque.contains(first)){
                set.remove(first);
            }
        }
    }
   System.out.println(max); 
 }

}