#include<iostream>
#include<set>
#include<vector>
using namespace std;
int main(){
int n;
cin>>n;
vector<int>v(n);
for(int i=0;i<n;i++){
cin>>v[i];
}
set<int>s(v.begin(),v.end());//set用法
cout<<s.size()<<endl;
for(int num:s){
cout<<num<<" ";
}
}