package Math.exercise;
import java.util.Scanner;
import java.util.TreeSet;

public class Main8 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        TreeSet<Integer> set=new TreeSet<>();
        int n=sc.nextInt();
        for(int i=0;i<n;i++){
            int a=sc.nextInt();
            set.add(a);
        }
        System.out.println(set.size());
        for (Integer i : set) {
            System.out.print(i+" ");
        }
    }
}