#include <bits/stdc++.h>
#define int long long
using namespace std;

vector<int> a;

signed main() {
	int n;
	cin >> n;

	for (int i = 1; i <= n; i++) {
		int x;
		cin >> x;
		a.push_back(x);
	}

	sort(a.begin(), a.end());
	a.erase(unique(a.begin(), a.end()), a.end());

	cout << a.size() << "\n";

//	for (auto x : a)
//		cout << x << " ";

	for (int i = 0; i < a.size(); i++) {
		cout << a[i] << " ";
	}
}