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

        int res = 0;
        for (int i = 0; i < n; i++) {
            int num = in.nextInt();
            deque.add(num);
            map.put(num, map.getOrDefault(num, 0)+1);
            if(deque.size()==m){
                res = Math.max(res, map.size());
                int frontElement = deque.poll();
                map.put(frontElement, map.get(frontElement)-1);
                if(map.get(frontElement)==0){
                    map.remove(frontElement);
                }
            }
        }
        System.out.println(res);
    }
}