#include <bits/stdc++.h>
using namespace std;
int n;
int cnt[1005]; // cnt[i] 统计出现了多少个 i
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        int x;
        cin >> x;
        cnt[x]++;
    }
    int ans = 0;
    for (int i = 1; i <= 1000; i++)
        if (cnt[i] > 0)
            ans++;
    cout << ans << "\n";
    for (int i = 1; i <= 1000; i++)
        if (cnt[i] > 0)
            cout << i << " ";
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int n;
int a[1123456];
int main()
{
    //输入
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    //排序
    sort(a + 1, a + n + 1);
    //输出
    int cnt=1;
    for(int i=2;i<=n;i++)
        if(a[i]!=a[i-1])
            cnt++;
    cout<<cnt<<"\n";
    for (int i = 1; i <= n; i++)
        if(i==1||a[i]!=a[i-1])
           cout << a[i] << " ";
    cout << "\n";
    return 0;
}