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