#include<iostream>
#include<algorithm>

using namespace std;

int main() {
    int n;
    cin >> n;
    int v[n];
    for (int i = 0; i < n; i++) {
        cin >> v[i];
    }
    sort(v, v + n);
    int m = unique(v, v + n) - v;
    cout << m << endl;
    for (int i = 0; i < m; i++) {
        cout << v[i] << " ";
    }
    cout << endl;
    return 0;
}