#include <iostream>
#include <algorithm>
using namespace std;
const int N(1003);
int num[N]={0},ans[103]={0};
int main()
{
	int n,x,m(0);
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>x;
		num[x]=1;
	}
	for(int i=1;i<=1000;i++)
		if(num[i])
		{
			m++;
			ans[m]=i;
		}
	cout<<m<<endl;
	cout<<ans[1];
	for(int i=2;i<=m;i++)
		cout<<" "<<ans[i];
	cout<<endl;
}
/**************************************************************
	Problem: 2260
	User: admin
	Language: C++
	Result: Accepted
	Time:48 ms
	Memory:2076 kb
****************************************************************/