学步园

#include <iostream>
#include <vector>
#include <set>
#include <algorithm>

using namespace std ;

int main()
{
	int m ;
	cin >> m ;
	int in ;
	set<int> num;
	for ( int i = 0 ; i < m ; ++i)
	{
	        cin >> in ;
	        num.insert(in);
    }
    cout << num.size() << endl;
    
	set<int>::iterator it;
    for ( it = num.begin();  it != num.end();++it)
	    cout << *it  << " " ;
	 
    cout << endl ;
    return 0 ;
}