#include <iostream>
using namespace std;
int n,m,c;
int a[105];
int main(){
    cin>>n;
	for(int i=0;i<=n;i++){
		cin>>m;
		a[m]++;
	}
    for(int i=0;i<=n;i++) if(a[i]>0) c++;
    cout<<c<<endl;
	for(int i=0;i<=n;i++){
		if(a[i]>0){
			cout<<i<<" ";
		}
	}
	return 0;
}#include <iostream>
using namespace std;
int n,m,c;
int a[105];
int main(){
    cin>>n;
	for(int i=0;i<=n;i++){
		cin>>m;
		a[m]++;
	}
    for(int i=0;i<=n;i++) if(a[i]>0) c++;
    cout<<c<<endl;
	for(int i=0;i<=n;i++){
		if(a[i]>0){
			cout<<i<<" ";
		}
	}
	return 0;
}