import java.util.*;
import java.util.stream.Collectors;
public class test {
        public static void main(String[] args) {
                Scanner in = new Scanner(System.in);
                Deque<Integer> deque = new ArrayDeque<>();
                Map<Integer,Integer> cnt = new HashMap<>();

                int n = in.nextInt();
                int m = in.nextInt();
                int mx = 0;
                in.nextLine();

                List<Integer> A = Arrays.stream(in.nextLine().trim().split("\\s+"))
                                .map(Integer::parseInt).collect(Collectors.toList());

                for (int i = 0; i < n; i++) {
                        deque.addLast(A.get(i));
                        cnt.put(A.get(i),cnt.getOrDefault(A.get(i), 0)+1);
                        if (deque.size()>m) {
                                int rm = deque.removeFirst();
                                cnt.put(rm,cnt.get(rm)-1);
                                if (cnt.get(rm) == 0) cnt.remove(rm);   
                        }
                     if (deque.size()== m) mx = Math.max(mx,cnt.size());
                }
                System.out.println(mx);
        }
}