# include <iostream>
# include <vector>
# include <algorithm>
using namespace std;
 
int main() {
	int n,x;
	cin >> n;
 
	int cnt = 1;
	vector <int> v;
	for (int i = 0; i < n; i++) {
		cin >> x;
		cnt += x == 4;
		v.push_back(x);
	}
 
	sort(v.rbegin(), v.rend());
	int sz = 4;
	bool f = false;
	for (int i = 0; i < n; i++) {
		if (v[i] != 4) {
			if (sz - v[i] < 0) {
				sz = 4 - v[i];		
				cnt++;
			} else sz -= v[i];
		}
	}
 
	cout << cnt;
	return 0;
}

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OAoyIDMgNCA0IDIgMSAzIDE=

8
2 3 4 4 2 1 3 1