#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 110;
int q[N], n;

void quick_sort(int q[], int l, int r) {
    if (l >= r) return;

    int x = q[l + r >> 1], i = l - 1, j = r + 1;
    while (i < j) {
        do i ++; while (q[i] < x);
        do j --; while (q[j] > x);
        if (i < j) swap(q[i], q[j]);
    }

    quick_sort(q, l, j);
    quick_sort(q, j + 1, r);
}

int main()
{
    cin >> n;
    for (int i = 0; i < n; i ++) cin >> q[i];

    quick_sort(q, 0, n - 1);

    int past = q[0], sum = 1;
    for (int i = 1; i < n; i ++) {
        if (q[i] != past) {
            sum ++;
            past = q[i];
        }
    }

    cout << sum << endl << q[0] << ' ';

    past = q[0];
    for (int i = 1; i < n; i ++) {
        if (q[i] != past) {
            cout << q[i] << ' ';
            past = q[i];
        }
    }

    return 0;
}