#include <bits/stdc++.h>

using namespace std;

int main() {
    int N;
    int x;
    set<int> set1;
    cin >> N;
    //输入
    for (int i = 0; i < N; i++) {
        cin >> x;
        set1.insert(x);
    }
    //输出个数
    cout << set1.size() << endl;
    //迭代器.输出每一个数值
    set<int>::iterator it;
    for (it = set1.begin(); it != set1.end(); it++)
        cout << *it << " ";
    cout << endl;
    return 0;
}