#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int i;
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<int> d(N + 1), e(N + 1);
  d[0] = 0;
  e[0] = 0;
  for (i = 1; i <= N; i++) {
    cin >> d[i];
    e[i] = d[i];
  }
  sort(d.begin(), d.end());
  sort(e.begin(), e.end());
  for (i = 1; i <= N; i++) {
    if (i % 2 == 1) {
      d[i] = min(d[i], 24 - d[i]);
    } else {
      d[i] = max(d[i], 24 - d[i]);
    }
  }
  int mn = 1e9;
  for (i = 1; i <= N; i++) {
    int x = abs(d[i] - d[i - 1]);
    mn = min(mn, min(x, 24 - x));
  }
  for (i = 1; i <= N; i++) {
    if (i % 2 == 1) {
      d[i] = max(d[i], 24 - d[i]);
    } else {
      d[i] = min(d[i], 24 - d[i]);
    }
  }
  int mnn = 1e9;
  for (i = 1; i <= N; i++) {
    int x = abs(d[i] - d[i - 1]);
    mnn = min(mnn, min(x, 24 - x));
  }
  cout << max(mn, mnn) << endl;
  return 0;
}
