#include <iostream>
#include <algorithm>
using namespace std;
const int N = 110;
int n;
int q[N];
int main()
{
cin >> n;
for (int i = 0; i < n; i ++ ) cin >> q[i];
sort(q, q + n);
//unique返回去重后不重复序列的最后一个位置q[k]
int k = unique(q, q + n) - q; //两指针相减得到两指针间元素个数
cout << k << endl;
for (int i = 0; i < k; i ++ ) cout << q[i] << ' ';
return 0;
}