#include <set>

#include <algorithm>

#include <iterator>

using namespace std;

int main(){

int n,total;

cin >> n;

int *ran = new int[n];

for(int i = 0; i < n; i++)

{

cin >> ran[i];

}

set<int> sran(ran, ran + n);

cout << sran.size() << endl;

ostream_iterator<int> out(cout, " ");

copy(sran.begin(),sran.end(), out);

return 0;

}