#include<iostream>
#include<algorithm>
using namespace std;
const int N = 110;
int a[N];
int n;
int main()
{
cin >> n;
for(int i = 0; i < n; i ++) cin >>a[i];
sort(a, a + n);
int cnt = 0;
for(int i = 0; i < n; i ++)
{
if(a[i] != a[i - 1])
cnt ++;
}
cout << cnt << endl;
cout << a[0] << ' ';
for(int i = 1; i < n; i ++)
{
if(a[i] != a[i - 1])
cout << a[i] << ' ';
}
cout << endl;
return 0;
}