public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        Deque<Integer> deque = new ArrayDeque<>();
        Map<Integer, Integer> numCount = new HashMap<>();
        int max = 0;
        int n = in.nextInt();
        int m = in.nextInt();

        for (int i = 0; i < n; i++) {
            int num = in.nextInt();
            deque.offerLast(num);
            numCount.merge(num, 1, Integer::sum);

            if (deque.size() > m) {
                Integer val = deque.pollFirst();
                if (numCount.merge(val, -1, Integer::sum) == 0) {
                    numCount.remove(val);
                }
            }

            if (deque.size() == m && numCount.size() > max) {
                max = numCount.size();
            }
        }

        in.close();

        System.out.println(max);
    }