include <bits/stdc++.h>

using namespace std; int n, a[1005], x, i, sum;

int main() {

cin >> n;
while (i != n) {
	i++;
	cin >> x;

	if (a[x] != 1) {
		a[x] = 1;
		sum++;
	} 
}
i = 0;
cout << sum << endl;
while (i != 1005) {

	if (a[i] > 0) {
		cout << i << " ";
	}
	i++;
}
return 0;

}