set

#include<bits/stdc++.h>
#include<set>
using namespace std;
const int N=100001;
int n,a[N];
int main(){
set<int>s;
cin>>n;
for(int i=1;i<=n;i++){
int t;
cin>>t;
s.insert(t);
}
cout<<s.size()<<endl;
for(auto x:s) cout<<x<<" ";
return 0;
}