#include <bits/stdc++.h> using namespace std; int main() { int a[1005],n,m=0; memset(a,0,sizeof(a)); cin>>n; for(int i=1;i<=n;i++){ int x; cin>>x; if(a[x]==0) m++; a[x]++; } cout<<m<<endl; for(int i=0;i<=1000;i++) if(a[i]>0) cout<<i<<" "; cout<<endl; return 0; }