#include
//#include<windows.h>
typedef long long ll;
using namespace std;
set<int> s1;
int main()
{
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		int temp;
		cin>>temp;
		s1.insert(temp); 
	}
	cout<<s1.size()<<endl;
	for(auto it:s1){
		cout<<it<<" ";
	}
	return 0;
}