#include<bits/stdc++.h>
using namespace std;
int main(){
  int i,n,m=0,j,s=0,x;
  bool a[1001]={0};
  cin>>n;
  for(i=0;i<n;i++){
  cin>>x;
  if(a[x]==0){
  a[x]=1;
  m++;}} 
  cout<<m<<endl;
  for(i=0;i<1001;i++){
  if(a[i]!=0) cout<<i<<endl;}
return 0;}
/**************************************************************
	Problem: 1183
	User: wtq001
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/