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