#include "bits/stdc++.h"

using namespace std;

void solve()
{
	int N;
	cin >> N;
	vector<int> s(12);
	int ans = 0;

	for (int i = 0; i < N; i++)
	{
		int d;
		cin >> d;
		if (d)
		{
			s[d-1]++;
			if (s[d-1]==3)
			{
				cout << 0 << endl;
				return;
			}
		}
		else
		{
			cout << 0 << endl;
			return;
		}
	}
	for (int bit = 0; bit < 1<<12; bit++)
	{
		vector<int> v;
		v.push_back(0);
		for (int i = 0; i < 12; i++)
		{
			if (!s[i]) continue;
			v.push_back((bit>>i&1)?i+1:23-i);
			if (s[i]>1) v.push_back((bit>>i&1)?23-i:i+1);
		}
		int n = v.size(), res = 12;
		for (int i = 0; i < n-1; i++)
			for (int j = i+1; j < n; j++)
			{
				int diff = abs(v[j]-v[i]);
				res = min(res, min(24-diff, diff));
			}
		ans = max(ans, res);
	}
	cout << ans << endl;
}

int main(void)
{
	solve();
	//cout << "yui(*-v・)yui" << endl;
	return 0;
}
