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


int main() {
	int N;
	cin>>N;
	int a[N] = {0};
	for(int i=0;i<N;i++)
	{
		cin>>a[i];
	}
	sort(a, a + N, less<int>() );  
	
	int n = unique(a, a + N) - a;
	
	cout<<n<<endl;
	
	for (int i = 0; i < n; i++)
	{
		cout << a[i] << " ";  
	}
	
	return 0;
}