#include <bits/stdc++.h>
using namespace std;
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define _rep(i,n) _repl(i,0,n)
#define rep(...) GET_MACRO(__VA_ARGS__, _repl, _rep)(__VA_ARGS__)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
void _dbg(string){cout<<endl;}
template<class H,class... T> void _dbg(string s,H h,T... t){int l=s.find(',');cout<<s.substr(0,l)<<" = "<<h<<", ";_dbg(s.substr(l+1),t...);}
template<class T,class U> ostream& operator<<(ostream &o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream &o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 1120000000

int main(){
  int n;
  cin>>n;
  vector<int> d(n);
  rep(i,n) cin>>d[i];

  if(n==1){
    cout << d[0] << endl;
    return 0;
  }

  vector<pair<int,int>> x;
  rep(i,n){
    x.pb(mp(d[i], i));
    if(d[i]!=0 && d[i]!=12) x.pb(mp(24-d[i], i));
  }
  sort(all(x));
dbg(x);
  for(int a = 12; a>=0; a--){
    auto f = [&](){
      vector<bool> used(n, false);
      int last = 0;
      int idx = 0;
      int m = x.size();
      while(idx < m){
        while(idx < m && (used[x[idx].second] || x[idx].first - last < a)) idx++;
        if(idx == m) break;
        // dbg(a,idx);
        last = x[idx].first;
        used[x[idx].second] = true;
        idx++;
      }
      if(24-last < a) return false;
      rep(i,n) if(!used[i]) return false;
      return true;
    };

    if(f()){
      cout << a << endl;
      return 0;
    }
  }
  assert(false);

  return 0;
}
