#include<iostream> using namespace std; int main() { int n,tmp,m = 0; cin >> n; int t[100001] = {}; for(int i = 0;i < n;i++){ cin >> tmp; t[tmp]++; if(t[tmp] == 1){ m++; } } cout << m << endl; for(int i = 0;i <= 10000;i++){ if(t[i] != 0){ cout << i <<" "; } } return 0; }