#include<iostream>
#include<algorithm>
using namespace std;
 int main(){

int a[100];
int n, sum=0;
cin >> n;
for (int i = 0; i < n; i++) {
	cin >> a[i];
}
sort(a, a + n);

for (int i = 0; i < n; i++) {
	if (a[i] != a[i + 1])
		sum++;
}
cout << sum << endl;

for (int i = 0; i < n; i++) {
	if (a[i] != a[i + 1])
		cout << a[i] << "  ";
}
return 0;
}