#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c[13] = {}, d[55];
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> d[i];
    c[d[i]]++;
  }
  if (c[0] >= 1 || c[12] >= 2) {
    cout << 0 << endl;
    return 0;
  }
  int s = 0;
  for (int i = 0; i <= 12; i++) {
    if (c[i] > 2) {
      cout << 0 << endl;
      return 0;
    }
    s += c[i];
  }
  int ans = 0;
  for (int i = 0; i < pow(2, n); i++) {
    vector<int> t;
    t.push_back(0);
    for (int j = 0; j < n; j++) {
      if (i & (1 << j))
        t.push_back(d[j]);
      else
        t.push_back(24 - d[j]);
    }
    sort(t.begin(), t.end());
    int mn = 24;
    for (int j = 0; j < n; j++) {
      mn = min(mn, t[j + 1] - t[j]);
    }
    mn = min(mn, 24 + t[0] - t[n]);
    ans = max(ans, mn);
  }
  cout << ans << endl;
}
