#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <utility>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef  long long ll;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define  MP make_pair
#define  PB push_back
#define inf  1000000007

int d[13];

int main(){
	int n;
	cin >> n;
	VI v(n);
	d[0]++;
	for(int i=0;i<n;i++){
		cin >> v[i];
		d[v[i]]++;
	}
	for(int i=0;i<13;i++){
		if(d[i]>2){
			cout << 0 << endl;
			return 0;
		}
	}
	VI a;
	int x = 0;
	for(int i=0;i<13;i++){
		if(d[i]==1){
			if(x==0){
				a.push_back(i);
				x = 1;
			}else{
				a.push_back(-i);
				x = 0;
			}
		}else if(d[i]==2){
			a.push_back(i);
			a.push_back(-i);
		}
	}
	int mi = 1000;
	for(int i=0;i<a.size();i++){
		for(int j=i+1;j<a.size();j++){
			int tmp = min(abs(a[i]-a[j]),24-abs(a[i]-a[j]));
			if(tmp < mi){
				mi  = tmp;
			}
		}
	}
	cout << mi << endl;
	return 0;
}