#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const double eps = 1e-10;
const int MOD = 1000000007;
const int INF = 1000000000;
const ll LINF = 1ll << 50;
template <typename T>
void printv(const vector<T>& s) {
  for (int i = 0; i < (int)(s.size()); ++i) {
    cout << s[i];
    if (i == (int)(s.size()) - 1)
      cout << endl;
    else
      cout << " ";
  }
}
int main() {
  cin.tie(0);
  cout << fixed << setprecision(10);
  int n;
  cin >> n;
  vector<int> d(n);
  for (int i = 0; i < n; ++i) {
    cin >> d[i];
    d[i] = min(d[i], 24 - d[i]);
  }
  sort(d.begin(), d.end());
  vector<int> t1(n + 1), t2(n + 1);
  t1[n] = 0;
  bool now = 0;
  for (int i = 0; i < n; ++i) {
    if (now) {
      t1[i] = d[i];
    } else {
      t1[i] = 24 - d[i];
    }
    now = !now;
  }
  t2[n] = 0;
  now = 1;
  for (int i = 0; i < n; ++i) {
    if (now) {
      t2[i] = d[i];
    } else {
      t2[i] = 24 - d[i];
    }
    now = !now;
  }
  sort(t1.begin(), t1.end());
  sort(t2.begin(), t2.end());
  int mi1 = 24 - t1[n - 1], mi2 = 24 - t2[n - 1];
  for (int i = 0; i < n; ++i) {
    mi1 = min(mi1, t1[i + 1] - t1[i]);
    mi2 = min(mi2, t2[i + 1] - t2[i]);
  }
  cout << max(mi1, mi2) % 24 << endl;
}
