#include <bits/stdc++.h>
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define RREP(i,a,b) for(int i=(a);i>=(b);i--)
#define pq priotity_queue
#define P pair<int,int>
#define P2 pair<int,P>
#define P3 pair<int,P2>
typedef long long ll; typedef long double ld;
using namespace std;
const int INF=1e9, MOD=1e9+7, around[]={0,1,1,-1,-1,0,-1,1,0,0};
const ll LINF=1e18;
const ld PI=abs(acos(-1));
int n,a,li[30];
vector<int> vec;

int main(){
	cin >> n; li[0]=true;
	REP(i,0,n){
		cin >> a;
		if(li[a] and li[24-a]){cout << 0 << endl; return 0;}
		else if(li[a] and !li[24-a]) li[24-a]=true;
		else li[a]=true; 
	}
	
	ll ei=0;
	REP(i,0,25) if(li[i] and li[24-i]) ei+=(1<<i);
	REP(i,0,25) if(li[i]) vec.push_back(i);
	sort(vec.begin(), vec.end());
	
	int ma=0;
	REP(i,0,(1<<vec.size())){
		if(ei&i) continue;
		set<int> st;
		vector<int> pos;
		bool f=false;
		int mi=INF;
		
		REP(j,0,vec.size()){
			if((i>>j)&1 and st.count(24-vec[j])){f=true; break;}
			else if((i>>j)&1) st.insert(24-vec[j]),pos.push_back(24-vec[j]);
			else if(st.count(vec[j])){f=true; break;}
			else st.insert(vec[j]),pos.push_back(vec[j]);
		}
		
		if(f) continue;
		sort(pos.begin(), pos.end());
		REP(i,0,pos.size()-1) mi=min(mi,pos[i+1]-pos[i]);
		mi=min(mi, min(abs(pos[pos.size()-1]-pos[0]), abs(24-(pos[pos.size()-1]-pos[0]))));

		ma=max(ma,mi);
	}
		
	cout << ma << endl;
	return 0;
}
