import java.util.*;

public class DemoTest5 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            int a =in.nextInt();
            int[] arr =new int[a];
            for(int i=0;i<a;i++){
                arr[i]=in.nextInt();
            }
            int c= in.nextInt();
            solve(arr,c);
        }
    }
    private static void solve(int[] arr,int c) {
        HashMap<Integer,Integer> map = new HashMap<>();
        for(int i = 0;i<arr.length;i++){
            map.put(arr[i],map.getOrDefault(arr[i],0)+1);
        }

        int count = 0;
        for(Map.Entry<Integer,Integer> entry:map.entrySet()){
            if(entry.getValue()>=c){
                count++;
            }
        }
        if(count == 0){
            System.out.println(0);
            return;
        }
        System.out.println(count);
        map.entrySet().stream().filter(entry-> entry.getValue()>=c).sorted((e1, e2)-> {
            if(Objects.equals(e2.getValue(), e1.getValue())){
                return e1.getKey()-e2.getKey();
            }else{
                return e2.getValue()-e1.getValue();
            }}).forEach(entry->{
            System.out.println(entry.getKey());
        });
    }
}