#include <iostream>
#include <set>
using namespace std;
int main(){
	set<int> s;
	int n;
	cin >> n;
	int tmp;
	for(int i = 0; i < n; i++){
		cin >> tmp;
		s.emplace(tmp);
	}
	cout << s.size() << endl;
	for(auto it = s.begin(); it != s.end(); it++){
		cout << *it << " ";
	}
	cout << endl;
	return 0;
}