#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("avx")
using namespace std;
template <typename T1, typename T2>
ostream& operator<<(ostream& o, const pair<T1, T2> p) {
  o << "(" << p.first << ":" << p.second << ")";
  return o;
}
template <typename iterator>
inline size_t argmin(iterator begin, iterator end) {
  return distance(begin, min_element(begin, end));
}
template <typename iterator>
inline size_t argmax(iterator begin, iterator end) {
  return distance(begin, max_element(begin, end));
}
template <typename T>
T& maxset(T& to, const T& val) {
  return to = max(to, val);
}
template <typename T>
T& minset(T& to, const T& val) {
  return to = min(to, val);
}
void bye(string s, int code = 0) {
  cout << s << endl;
  exit(0);
}
mt19937_64 randdev(8901016);
inline long long int rand_range(long long int l, long long int h) {
  return uniform_int_distribution<long long int>(l, h)(randdev);
}
namespace {
class MaiScanner {
 public:
  template <typename T>
  void input_integer(T& var) {
    var = 0;
    T sign = 1;
    int cc = getchar_unlocked();
    for (; cc < '0' || '9' < cc; cc = getchar_unlocked())
      if (cc == '-') sign = -1;
    for (; '0' <= cc && cc <= '9'; cc = getchar_unlocked())
      var = (var << 3) + (var << 1) + cc - '0';
    var = var * sign;
  }
  inline int c() { return getchar_unlocked(); }
  inline MaiScanner& operator>>(int& var) {
    input_integer<int>(var);
    return *this;
  }
  inline MaiScanner& operator>>(long long& var) {
    input_integer<long long>(var);
    return *this;
  }
  inline MaiScanner& operator>>(string& var) {
    int cc = getchar_unlocked();
    for (; !(0x21 <= (cc) && (cc) <= 0x7E); cc = getchar_unlocked())
      ;
    for (; (0x21 <= (cc) && (cc) <= 0x7E); cc = getchar_unlocked())
      var.push_back(cc);
    return *this;
  }
  template <typename IT>
  void in(IT begin, IT end) {
    for (auto it = begin; it != end; ++it) *this >> *it;
  }
};
}  // namespace
MaiScanner scanner;
long long int n;
int dd[55];
inline int diff(int t1, int t2) {
  return min({abs(t2 - t1), abs(t2 - t1 - 24), abs(t2 - t1 + 24)});
}
void zipp() {
  map<int, int> zip;
  for (auto i = 0ll; (i) < (n); ++(i)) {
    zip[dd[i]]++;
  }
  int m = 0;
  for (auto p : zip) {
    if (p.second >= 3) bye("0");
    for (auto i = 0ll; (i) < (min(2, p.second)); ++(i)) dd[m++] = p.first;
  }
  n = m;
}
void guchoku() {
  int ww[30];
  int best = 0;
  ww[0] = ww[24] = 1;
  for (int bit = 0; bit < 1 << n; ++bit) {
    int b = bit;
    fill(ww + 1, ww + 24, 0);
    for (auto i = 0ll; (i) < (n); ++(i)) {
      ww[(b & 1) ? dd[i] : 24 - dd[i]] = 1;
      b >>= 1;
    }
    int nice = 25;
    int last = 0;
    for (auto i = 0ll; (i) < (25); ++(i)) {
      if (!ww[i]) continue;
      minset(nice, int(i) - last);
      last = i;
    }
    maxset(best, nice);
  }
  cout << best << endl;
}
void my_nice_solution() {}
int main() {
  scanner >> n;
  scanner.in(dd, dd + n);
  if (n == 1) {
    cout << diff(0, dd[0]) << endl;
    return 0;
  }
  zipp();
  if (n <= 26) {
    guchoku();
  } else {
    abort();
    my_nice_solution();
  }
  return 0;
}
