#include <bits/stdc++.h>
using namespace std;
using ll = int64_t;
int cnt[12 + 1] = {1};
int dfs(int num, vector<int> v) {
  if (num == 13) {
    sort(v.begin(), v.end());
    int ret = 1e5;
    for (int i = 0; i < v.size() - 1; ++i)
      ret = min(ret, (int)abs(v[i] - v[i + 1]));
    ret = min(ret, (int)abs(v[v.size() - 1] - v[0]));
    return ret;
  }
  if (!cnt[num]) {
    return dfs(num + 1, v);
  } else if (cnt[num] == 2) {
    v.push_back(num);
    v.push_back(24 - num);
    return dfs(num + 1, v);
  } else {
    vector<int> tmp = v;
    tmp.push_back(num);
    int ret = dfs(num + 1, tmp);
    v.push_back(24 - num);
    ret = max(ret, dfs(num + 1, v));
    return ret;
  }
}
int main() {
  int n;
  cin >> n;
  int d[n];
  for (int i = 0; i < n; ++i) cin >> d[i];
  for (int i = 0; i < n; ++i) {
    ++cnt[d[i]];
    if (cnt[d[i]] >= 3 || !d[i]) {
      cout << 0 << endl;
      return 0;
    }
  }
  vector<int> v;
  v.push_back(0);
  cout << dfs(1, v) << endl;
  return 0;
}
