#include <bits/stdc++.h>
using namespace std;
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T>
inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <typename T>
T gcd(T x, T y) {
  if (y == 0)
    return x;
  else
    return gcd(y, x % y);
}
template <typename T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <typename T>
bool is_prime(T n) {
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0) return false;
  }
  return n != 1;
}
map<int, int> prime_factor(int n) {
  map<int, int> res;
  for (int i = 2; i * i <= n; i++) {
    while (n % i == 0) {
      ++res[i];
      n /= i;
    }
  }
  if (n != 1) res[n] = 1;
  return res;
}
int extgcd(int a, int b, int& x, int& y) {
  int d = a;
  if (b != 0) {
    d = extgcd(b, a % b, y, x);
    y -= (a / b) * x;
  } else {
    x = 1;
    y = 0;
  }
  return d;
}
long long mod_pow(long long x, long long n, long long mod) {
  if (n == 0) return 1;
  long long res = mod_pow(x * x % mod, n / 2, mod);
  if (n & 1) res = res * x % mod;
  return res;
}
vector<string> split(const string& str, char delim) {
  vector<string> res;
  size_t current = 0, found;
  while ((found = str.find_first_of(delim, current)) != string::npos) {
    res.push_back(string(str, current, found - current));
    current = found + 1;
  }
  res.push_back(string(str, current, str.size() - current));
  return res;
}
bool is_kadomatsu(int a, int b, int c) {
  if (a == b || a == c || b == c) return false;
  if (a > b && c > b) return true;
  if (a < b && c < b) return true;
  return false;
}
struct UF {
  int n;
  vector<int> d;
  UF() {}
  UF(int n) : n(n), d(n, -1) {}
  int root(int v) {
    if (d[v] < 0) return v;
    return d[v] = root(d[v]);
  }
  bool same(int a, int b) { return root(a) == root(b); }
  bool unite(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y) return false;
    if (size(x) < size(y)) swap(x, y);
    d[x] += d[y];
    d[y] = x;
    return true;
  }
  int size(int v) { return -d[root(v)]; }
};
vector<int> divisor(int n) {
  if (n == 1) return {};
  vector<int> res;
  for (int i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      res.emplace_back(i);
      if (i != 1 && i != n / i) res.emplace_back(n / i);
    }
  }
  return res;
}
struct Bellmanford {
  int n;
  struct edge {
    int from, to, cost;
  };
  vector<edge> E;
  vector<int> d;
  Bellmanford(int n) : n(n), d(n) { E.resize(n); }
  void add_edge(int x, int y, int cost) {
    edge e;
    e.from = x;
    e.to = y;
    e.cost = cost;
    E.push_back(e);
  }
  void shortest_path(int s) {
    for (int i = (0); i < (n); ++i) d[i] = (1000000000);
    d[s] = 0;
    while (true) {
      bool update = false;
      for (auto e : E) {
        if (d[e.from] != (1000000000) && d[e.to] > d[e.from] + e.cost) {
          d[e.to] = d[e.from] + e.cost;
          update = true;
        }
      }
      if (!update) break;
    }
  }
};
struct Dijkstra {
  int n;
  struct edge {
    int to;
    long long cost;
  };
  vector<vector<edge>> G;
  vector<long long int> d;
  Dijkstra(int n) : n(n), d(n) { G.resize(n); }
  void add_edge(int x, int y, long long cost) {
    edge e;
    e.to = y;
    e.cost = cost;
    G[x].push_back(e);
  }
  void shortest_path(int s) {
    for (int i = (0); i < (n); ++i) d[i] = 100000000000000000;
    d[s] = 0;
    priority_queue<pair<long long, int>, vector<pair<long long, int>>,
                   greater<pair<long long, int>>>
        que;
    que.push(make_pair(0, s));
    while (!que.empty()) {
      pair<int, int> p = que.top();
      que.pop();
      int v = p.second;
      if (d[v] < p.first) continue;
      for (auto e : G[v]) {
        if (d[e.to] > d[v] + e.cost) {
          d[e.to] = d[v] + e.cost;
          que.push(make_pair(d[e.to], e.to));
        }
      }
    }
  }
};
struct Segmenttree {
  int n;
  vector<pair<long long, int>> dat;
  Segmenttree() {}
  void init(long long n_) {
    n = 1;
    while (n < n_) n *= 2;
    dat.resize(2 * n - 1);
    for (int i = (0); i < (2 * n - 1); ++i)
      dat[i] = pair<long long, int>(-(1000000000), -(1000000000));
  }
  void update(int idx, long long val) {
    idx += n - 1;
    dat[idx] = make_pair(val, -(idx - n + 1));
    while (idx > 0) {
      idx = (idx - 1) / 2;
      dat[idx] = max(dat[idx * 2 + 1], dat[idx * 2 + 2]);
    }
  }
  pair<long long, int> query(int a, int b) { return query_seg(a, b, 0, 0, n); }
  pair<long long, int> query_seg(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l)
      return pair<long long, int>(-(1000000000), -(1000000000));
    if (a <= l && r <= b)
      return dat[k];
    else {
      return max(query_seg(a, b, k * 2 + 1, l, (l + r) / 2),
                 query_seg(a, b, k * 2 + 2, (l + r) / 2, r));
    }
  }
};
int main() {
  int n;
  cin >> n;
  vector<int> timeb(n);
  for (int i = (0); i < (n); ++i) {
    int t;
    cin >> t;
    timeb[i] = t;
  }
  if (n == 1) {
    cout << (min(timeb[0], 24 - timeb[0])) << endl;
    ;
    return 0;
  }
  sort((timeb).begin(), (timeb).end());
  for (int i = (0); i < (n - 2); ++i) {
    if (timeb[i] == timeb[i + 1] && timeb[i + 1] == timeb[i + 2]) {
      cout << (0) << endl;
      ;
      return 0;
    }
  }
  n = timeb.size();
  int ans = 0;
  for (int i = (0); i < (1 << n); ++i) {
    vector<int> tmp(n);
    for (int j = (0); j < (n); ++j) {
      if ((i >> j) & 1) {
        tmp[j] = timeb[j];
      } else {
        tmp[j] = 24 - timeb[j];
      }
    }
    int tmpa = 500;
    for (int j = (0); j < (n - 1); ++j) {
      tmpa = min(tmpa, abs(tmp[j] - tmp[j + 1]));
    }
    ans = max(tmpa, ans);
  }
  cout << (ans) << endl;
  ;
  return 0;
}
