#include<iostream> 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]++; } 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 <<" "; } } }