#include <bits/stdc++.h>
using namespace std;
string DBG_DLM(int& i) { return (i++ == 0 ? "" : ", "); }
template <class T>
ostream& operator<<(ostream& os, vector<T> v);
template <class T>
ostream& operator<<(ostream& os, set<T> v);
template <class T>
ostream& operator<<(ostream& os, queue<T> q);
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q);
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p);
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> mp);
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> mp);
template <int I, class TPL>
void DBG(ostream& os, TPL t) {}
template <int I, class TPL, class H, class... Ts>
void DBG(ostream& os, TPL t) {
  os << (I == 0 ? "" : ", ") << get<I>(t);
  DBG<I + 1, TPL, Ts...>(os, t);
}
template <class T, class K>
void DBG(ostream& os, pair<T, K> p, string delim) {
  os << "(" << p.first << delim << p.second << ")";
}
template <class... Ts>
ostream& operator<<(ostream& os, tuple<Ts...> t) {
  os << "(";
  DBG<0, tuple<Ts...>, Ts...>(os, t);
  os << ")";
  return os;
}
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p) {
  DBG(os, p, ", ");
  return os;
}
template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : v) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, set<T> s) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : s) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.front();
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.top();
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using vs = vector<string>;
using vvs = vector<vs>;
using vvvs = vector<vvs>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vvvd = vector<vvd>;
using vpii = vector<pii>;
using vvpii = vector<vpii>;
using vvvpii = vector<vvpii>;
template <class A, class B>
bool amax(A& a, const B& b) {
  return b > a ? a = b, 1 : 0;
}
template <class A, class B>
bool amin(A& a, const B& b) {
  return b < a ? a = b, 1 : 0;
}
ll ri() {
  ll l;
  cin >> l;
  return l;
}
string rs() {
  string s;
  cin >> s;
  return s;
}
ll solve() {
  int n = ri();
  vector<int> A(n);
  for (int i = int(0); i < int(n); ++i) A[i] = ri();
  sort((A).begin(), (A).end());
  vi C(13);
  for (auto&& a : A) C[a]++;
  vi fix(25);
  vi non;
  if (C[0] > 0) return 0;
  if (C[12] >= 2) return 0;
  for (int i = int(0); i < int(13); ++i) {
    if (C[i] >= 3) return 0;
    if (C[i] == 2) {
      fix[C[i]] = 1;
      fix[24 - C[i]] = 1;
    }
    if (C[i] == 1) {
      non.emplace_back(i);
    }
  };
  ;
  int m = ((int)(non).size());
  int ans = 0;
  for (int mask = int(0); mask < int((1LL << (m))); ++mask) {
    vi T(fix);
    T[0] = T[24] = 1;
    bool ok = 1;
    for (int j = int(0); j < int(m); ++j) {
      int s = non[j];
      int t = ((1LL << (j)) & mask) ? t = s : 24 - s;
      if (T[t]) {
        ok = 0;
        break;
      }
      T[t] = 1;
    };
    if (ok) {
      int cand = 12;
      vi X;
      for (int x = int(0); x < int(25); ++x) {
        if (T[x]) X.emplace_back(x);
      }
      int k = ((int)(X).size());
      for (int j = int(0); j < int(k - 1); ++j) {
        amin(cand, X[j + 1] - X[j]);
      }
      amax(ans, cand);
    }
  }
  return ans;
}
void Main() { cout << solve() << endl; }
signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  Main();
  return 0;
}
