rt

#include<iostream>
using namespace std;
bool tong[1010];
int sum;
int main(){
    int a;
    cin>>a;
    int j;
    for(int i=1;i<=a;i++){
        cin>>j;
        tong[j]=true;
    }
    for(int i=1;i<=a;i++){
        if(tong[i])sum++;
    }
    cout<<sum<<endl;
    for(int i=1;i<=a;i++){
        if(tong[i])cout<<i<<" ";
    }
    return 0;
}