# include<iostream> using namespace std; int n,a[1001],x,n1; int main(){ cin>>n; n1=n; for(int i=1;i<=n1;i++){ cin>>x; a[x]++; } for(int i=1;i<=1000;i++){ if(a[i]>1)n=n-a[i]+1; } cout<<n<<endl; for(int i=1;i<=1000;i++){ if(a[i]>0){ cout<<i<<" "; } } return 0; }