#include<iostream>
#include<algorithm>
using namespace std;
const int N = 110;
int q[N];
int main()
{
    int n;
    cin >> n;
    for(int i = 0; i < n; i++) cin >> q[i];

    sort(q, q + n);

    int  t = unique(q, q + n) - q;

    cout << t << endl;

    for(int i = 0; i < t; i++) cout << q[i] << " ";

    return 0;
}