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