#define _CRT_SECURE_NO_WARNINGS

#include<iostream>
#include<cstdio>
using namespace std;

int main(){
	int n; cin >> n;
	int num[1001] = { 0 };
	int tmp, count = 0;
	for (int i = 1; i <= n; i++){
		cin >> tmp;
		num[tmp] = 1;
	}
	for (int i = 1; i <= 1001; i++)
	if (num[i] == 1)
		count++;
	cout << count << endl;
	for (int i = 1; i <= 1001; i++)
	if (num[i] == 1)
		cout << i << ' ';
	getchar();
	return 0;
}