#include <bits/stdc++.h>
using namespace std;
#define modulo 1000000007
#define mod(mod_x) ((((long long)mod_x)+modulo)%modulo)
#define Inf 1000000000000000000

int main(){
	
	int N;
	cin>>N;
	
	vector<int> D(N+1);
	D[N]=0;
	for(int i=0;i<N;i++){
		cin>>D[i];
	}
	
	map<int,int> mp;
	for(int i=0;i<=N;i++){
		mp[D[i]]++;
	}
	
	if(mp[0]>=2){
		cout<<0<<endl;
		return 0;
	}
	if(mp[12]>=2){
		cout<<0<<endl;
		return 0;
	}
	
	vector<int> A;
	for(int i=0;i<=12;i++){
		if(mp[i]>=3){
			cout<<0<<endl;
			return 0;
		}
		for(int j=0;j<mp[i];j++){
			A.push_back(i);
		}
	}
	if(A.size()>=13){
		cout<<1<<endl;
		return 0;
	}
	int ans = 0;
	for(int i=0;i<(1<<A.size());i++){
		vector<int> B(A.size());
		for(int j=0;j<A.size();j++){
			if((i>>j)&1){
				B[j] = A[j];
			}
			else{
				B[j] = 24-A[j];
			}
		}
		sort(B.begin(),B.end());
		int k = 99;
		for(int j=0;j<B.size();j++){
			if(j==0){
				k = min(k,24-B[B.size()-1]);
			}
			else{
				k = min(k,B[j]-B[j-1]);
			}
		}
		ans = max(k,ans);
	}
	
	cout<<ans<<endl;
	
	
	
	
	return 0;
}
