//丹阳新区实小路彦
#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n, b = 0;
    cin >> n;
    int a[n];
    for (int i = 0; i < n; i++)
        cin >> a[i];
    for (int i = 0; i < n; i++)
        for(int j = 0; j < n; j++)
            if (a[i] < a[j]) swap(a[i], a[j]);
    for (int i = 0; i < n; i++)
        if (a[i] == a[i + 1])
        {
            a[i] = 0;
            b++;
        }
    cout << n - b << endl;
    for (int i = 0; i < n; i++)
        if (a[i] != 0) cout << a[i] << " ";
    return 0;
}