#include<iostream>
#include<algorithm>
#include<cassert>
#include<vector>
#include<fstream>
#include<string>
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<queue>
#include<map>

using namespace std;
#define REP(i,m,n) for(long long i=m;i<n;++i)
#define INF 10000000000000000
#define MOD 1000000007
#define ll long long
#define mp make_pair
#define all(v) v.begin(),v.end()

vector<int>v(13, 0);
vector<int>ans, hoge;

int main() {
	int n;
	cin >> n;
	v[0]++;
	REP(i, 0, n) {
		int tmp;
		cin >> tmp;
		v[tmp]++;
	}
	REP(i, 1, 12) {
		if (v[i] > 2) {
			cout << 0 << endl; return 0;
		}
	}
	if (v[0] >= 2) {
		cout << 0 << endl; return 0;
	}
	if (v[12] >= 2) {
		cout << 0 << endl; return 0;
	}
	REP(i, 1, 12) {
		if (v[i] == 2) {
			if (v[i - 1] == 1 || v[i + 1] == 1) {
				cout << 1 << endl; return 0;
			}
		}
	}
	if (v[1] == 1) {
		cout << 1 << endl; return 0;
	}
	if (v[12] == 1) {
		if (v[11] == 1) {
			cout << 1 << endl; return 0;
		}	
	}
	REP(i, 0, 13) {
		REP(j, 0, v[i]) {
			hoge.push_back(i);
		}
	}
	REP(i, 0, hoge.size()) {
		if (i % 2 == 1) {
			ans.push_back(24 - hoge[i]);
		}
		else {
			ans.push_back(hoge[i]);
		}
	}
	sort(all(ans));
	int diff = hoge[1];
	REP(i, 1, ans.size()) {
		diff = min(diff, ans[i] - ans[i - 1]);
	}
	cout << diff << endl;
	return 0;
}