#include <bits/stdc++.h>
using namespace std;
using Int = int_fast64_t;
Int n, ans = 1e9;
vector<Int> a(1, 0);
vector<Int> b(24);
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  for (Int i = 0; i < n; ++i) {
    Int t;
    cin >> t;
    a.push_back(t);
  }
  sort(a.begin(), a.end());
  for (size_t i = 0; i < a.size(); ++i) {
    if (i % 2 == 0) {
      if (b[a[i]] > 0) {
        cout << 0 << "\n";
        return 0;
      } else {
        ++b[a[i]];
      }
    } else {
      if (b[(24 - a[i]) % 24] > 0) {
        cout << 0 << "\n";
        return 0;
      } else {
        ++b[24 - a[i]];
      }
    }
  }
  for (Int i = 0; i < 23; ++i)
    for (Int j = i + 1; j < 24; ++j)
      if (b[i] & b[j]) ans = min(ans, j - i);
  cout << ans << "\n";
}
