!!!!!!!!!!!!!!!!!!!!

#include<bits/stdc++.h>
using namespace std;
int 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 i:s) cout<<i<<" ";
return 0;
}