import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Deque<Integer> deque = new LinkedList<>();
        
        int n = sc.nextInt();
        int m = sc.nextInt();
        int maxUniqueNumbers = 0;
        
        Map<Integer, Integer> frequencyMap = new HashMap<>(n);
                
        for (int i = 0; i < n; i++) {
            
            int currentInt = sc.nextInt();
            deque.addLast(currentInt);
            frequencyMap.compute(currentInt, (k, v) -> Objects.isNull(v) ? 1 : v+1);
            
            if (deque.size() != m) continue;
                
            if (frequencyMap.size() > maxUniqueNumbers) maxUniqueNumbers = frequencyMap.size();
            
            frequencyMap.compute(deque.pollFirst(), (k, v) -> v <= 1 ? null : v-1);
            
        }
            
        System.out.println(maxUniqueNumbers);
    }
}