#include <iostream>
#include <algorithm>
using namespace std;
int n,tmp,cnt,arr[101];
bool boo[1001];
int main (){
cin>>n;
for (int i = 0;i < n;i++){
cin>>tmp;
if (boo[tmp] == 1) continue;//打上flag的跳过
boo[tmp] = 1;//给已出现的打上flag
arr[cnt++] = tmp;
}
sort(arr,arr + cnt);
cout<<cnt<<endl;
for (int i = 0;i < cnt;i++) cout<<arr[i]<<' ';
return 0;
}