#include <bits/stdc++.h>

using namespace std;
const int N = 1010;
int a[N];
int b[N], bl;
int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) cin >> a[i];
    sort(a, a + n);
    int pre = -1;
    for (int i = 0; i < n; i++) {
        if (a[i] != pre) {
            pre = a[i];
            b[++bl] = a[i];
        }
    }
    cout << bl << endl;
    for (int i = 1; i <= bl; i++) cout << b[i] << " ";
    return 0;
}