#include<bits/stdc++.h> using namespace std; int a[1001]; int main(){ int n,k,sum = 0; cin >> n; for(int i =1;i <= n;i++){ cin >> k; if(a[k]== 0){ a[k] = 1; sum++; } } cout << sum << endl; for(int j =1;j <= 1000;j++){ if(a[j] != 0){ cout << j << " "; } } return 0; }