#include<bits/stdc++.h>
#define INF 1e9
#define llINF 1e18
#define MOD 1000000007
#define pb push_back
#define mp make_pair 
#define F first
#define S second
#define ll long long
#define vi vector<ll>
#define vvi vector<vi>
#define substr(s,f,t) (s.substr(f-1,t-f+1))
#define ALL(a) (a).begin(),(a).end()
#define Yes(hoge) cout<<((hoge)?"Yes":"No")<<endl;
#define YES(hoge) cout<<((hoge)?"YES":"NO")<<endl;
using namespace std;
struct Grid{ll x,y,t;};
struct Edge{ll to,cost;};
struct Graph{vector<vector<Edge>>E;int V;
  const ll Inf = llINF;const int MAX_V=201010;vector<ll>d;
  Graph(int n):E(n){d.resize(MAX_V);E.resize(n);V=n;}
  void init(){for(int i=0;i<MAX_V;i++)d[i]=Inf;}
  void add_edge(ll from,ll to,ll cost){E[from].pb({to,cost});}
};
int n;
int dep;
int ans=0;
set<int>se;
void dfs(int bit,int d){
  if(de==d){
    vi ho;
    int cnt=0;
    for(int num:se){
      if(bit&(1<<cnt)){
	ho.pb((24-num)%24);
      }else{
	ho.pb(num);
      }
      cnt++;
    }
    ll mi=INF;
    for(int i=0;i<dep;i++)
      for(int j=i+1;j<dep;j++)
	mi=min(mi,abs(ho[i]-ho[j]));
    ans=max(ans,mi);
  }
  
  dfs(bit+1<<d,d+1);
  dfs(bit,d+1);
}
int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin>>n;
  se.insert(0);
  for(int i=1;i<=n;i++){int a;cin>>a;se.insert(a);}
  dep=se.size();
  dfs(0,0);
  cout<<ans<<endl;
  return 0;
}
