#include <iostream>

#include <map>

#include <fstream>

using namespace std;

struct classcomp{

 bool operator() (const int& a, const int& b){

 return a < b;

 }

};

int n,m;

map<int,int,classcomp> p;

int ain()

{

 freopen("random.in","r",stdin);

 freopen("random.out","w",stdout);

 scanf("%d",&n);

 for (int i=1;i<=n;i++)

 {

 scanf("%d",&m);

 p.insert(pair<int,int>(m,1));

 }

 map<int,int>::iterator i;

 i=p.begin();

 printf("%d\n",p.size());

 for (;i!=p.end();i++)

 printf("%d ",i->first);

 return 0;

}

int ass=ain();

int main(){;

}

}