set题解

#include <bits/stdc++.h>

using namespace std;

long long n;

int main( ) {
	set<long long> s;
	cin >> n;
	
	for (int i = 1 ; i <= n ; i++ ) {
		long long x;
		cin >> x;
		s.insert(x);
	}
	
	cout << s.size() << endl;
	
	for (auto i : s) cout << i << " ";
	
	return 0;
}