#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <algorithm>
#include <cstdlib>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <iostream>
#include <cassert>
 
#pragma comment(linker, "/STACK:336777216")  
 
using namespace std;

const int MAXN = 200000 + 10;
const int INF = 1000000000;

int N;
int cnt[13];
int used[24];
int ans;

void DFS(int i)
{
	if (i == 13)
	{
		int cur = 100;
		for (int a = 0; a < 24; a ++)
		{
			if (used[a])
			{
				for (int b = 1; b <= 24; b ++)
					if (used[(a + b) % 24] || used[(a - b + 24) % 24])
					{
						cur = min(cur, b);
						break;
					}
			}
		}
		if (cur > ans) ans = cur;
		return;
	}
	if (cnt[i] == 0)
		DFS(i + 1);
	else if (cnt[i] == 2)
	{
		used[i] = used[24 - i] = 1;
		DFS(i + 1);
		used[i] = used[24 - i] = 0;
	}
	else
	{
		used[i] = 1;
		DFS(i + 1);
		used[i] = 0;
		if (i != 0)
		{
			used[24 - i] = 1;
			DFS(i + 1);
			used[24 - i] = 0;
		}
	}
}

void Work()
{
	scanf("%d", &N);
	cnt[0] = 1;
	for (int i = 0; i < N; i ++)
	{
		int d;
		scanf("%d", &d);
		cnt[d] ++;
	}
	if (cnt[0] > 1 || cnt[12] > 1)
	{
		printf("0\n");
		return;
	}
	for (int i = 1; i <= 11; i ++)
		if (cnt[i] > 2)
		{
			printf("0\n");
			return;
		}
	ans = 0;
	DFS(0);
	printf("%d\n", ans);
}

int main()
{
	Work();
	return 0;
}
