#include<iostream> #include<cmath> #include<iomanip> using namespace std; int main() { int a[1001] = {0}; int n, s; cin >> n; for (int i = 1; i <= n; i++) { cin >> s; a[s]++; //TODO } int count = 0; for (int i = 0; i <= 1000; i++) { if (a[i] != 0) { count++; //TODO } } cout << count<<endl; for (int i = 0; i <= 1000; i++) { if (a[i] != 0) { cout << i << " "; } } }