#include <iostream>
#include <set>
using namespace std;

int main() {
    int N;
    cin >> N;
    
    set<int> nums;
    for(int i = 0; i < N; i++) {
        int num;
        cin >> num;
        nums.insert(num);
    }
    
    cout << nums.size() << endl;
    for(auto it = nums.begin(); it != nums.end(); it++) {
        if(it != nums.begin()) cout << " ";
        cout << *it;
    }
    return 0;
}