#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<<" "; } } }