include

include <bits/stdc++.h>

include

include

using namespace std;

int main() {

int n;
cin >> n;
unordered_set <int> c;
for(int i = 0; i < n; ++i){
	int k;
	cin >> k;
	c.insert(k);
}
cout << min(int(c.size()), n / 2);

return 0;

}