#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v1(25, 0);
  v1[0] = v1[24] = 1;
  for (int(i) = 0; (i) < (n); ++(i)) {
    int d;
    cin >> d;
    ++v1[d];
  }
  if (v1[0] > 1) {
    cout << 0 << endl;
    return 0;
  }
  int res = 0;
  for (int(i) = 0; (i) < (pow(2, 12)); ++(i)) {
    vector<int> v = v1;
    for (int(j) = 0; (j) < (12); ++(j)) {
      if (((i >> j) & 1) && v[j] > 0) {
        --v[j];
        ++v[24 - j];
      }
    }
    int mn = 12;
    if (i == pow(2, 11)) {
      int a = 0;
    }
    for (int j = 1; j < 25; ++j) {
      int cnt = 0;
      if (v[j] > 1)
        mn = 0;
      else {
        while (j < 25 && v[j] == 0) {
          ++cnt;
          ++j;
        }
        if (v[j] > 1) mn = 0;
      }
      mn = min(mn, cnt + 1);
    }
    res = max(res, mn);
  }
  cout << res << endl;
}
