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#include<bits/stdc++.h>
using namespace std;
int main(){
bool book[1001]={0};
int n;
int final=0;
cin>>n;
int a[n];
for(int i=0;i<n;i++){
cin>>a[i];
if(book[a[i]]==0){
final++;
}
book[a[i]]=1;
}
cout<<final<<endl;
for(int i=1;i<=1000;i++){
if(book[i]==1){
cout<<i<<" ";
}
}
return 0;
}