C++ :

#include <bits/stdc++.h>
using namespace std;

int main() {
	int n, x;
	set <int> s;
	set <int> :: iterator it;
	
	while (cin >> n) {
		if (n == 0) break;
		
		s.clear();
		while (n --) {
			cin >> x;
			s.insert(x);
		}
		
		cout << s.size() << endl;
		for (it = s.begin(); it != s.end(); it ++) cout << *it << ' ';
		cout << endl << endl;
	}

	return 0;
}