#include<bits/stdc++.h>
using namespace std;
int main()
{
	freopen("random.in","r",stdin);
	freopen("random.out","w",stdout);
	int n;
	cin>>n;
	set<int> s;
	for(int i=1;i<=n;i++)
	{
		int a;
		cin>>a;
		s.insert(a);
	}
	cout<<s.size()<<endl;
	for(auto x:s)
	{
		cout<<x<<" ";
	}
	return 0;
}