#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
int main(){
	int i,j,n,d[30],s = 0,c[30]={0};
	cin >> n;
	if(n>23){
		cout << 0 << endl;
		return 0;
	}
	
	for(i=0;i<n;i++){
		cin >> d[i];
		c[d[i]]++;
		if(!d[i]){
			cout << 0 << endl;
			return 0;
		}
	}
	
	for(i=1;i<=11;i++){
		if(c[i]>=3 || c[12]>=2){
			cout << 0 << endl;
			return 0;
		}
	}
	
	if(n==23){
		cout << 1 << endl;
		return 0;
	}
	
	for(i=0;i<(1<<n);i++){
		vector<int> v;
		for(j=0;j<n;j++){
			if(i & 1<<j){
				v.push_back((d[j]+12)%24);
			}else{
				v.push_back(12-d[j]);
			}
		}
		v.push_back(12);
		sort(v.begin(),v.end());
		int x = (24 + v[0] - v.back())%24;
		for(j=0;j<v.size()-1;j++){
			x = min(x,v[j+1]-v[j]);
		}
		s = max(s,x);
	}
	cout << s << endl;
}