#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;
}