#include <iostream> using namespace std; int main() { int n,s,cnt = 0; cin>>n; int a[10000] = {0}; for(int i=1;i<= n;i++){ cin>>s; a[s]++; } for(int i=0;i<=1000;i++){ if(a[i] != 0){ cnt++; } } cout<<cnt<<endl; for(int i=0;i<=1000;i++){ if(a[i] != 0){ cout<<i<<" "; } } }