#include <iostream> using namespace std; int main() { int n, tmp, ans = 0; int cnt[1001] = {}; cin >> n; while (n--) { cin >> tmp; cnt[tmp]++; if (cnt[tmp] == 1) ans++; } cout << ans << endl; int i = 1; while (cnt[i] == 0) i++; cout << i; for (i = i + 1; i < 1001; i++) if (cnt[i] > 0) cout << " " << i; cout << endl; return 0; }