#include <bits/stdc++.h>
using namespace std;
int solve(int s, int N, vector<int> &D, vector<int> t, int d) {
  if (s == N || d == 0) return d;
  int x = D[s], y = (24 - D[s]) % 24, d1 = d, d2 = d;
  for (int i = 0; i <= s; ++i) {
    d1 = min(d1, abs(t[i] - x));
    d2 = min(d2, abs(t[i] - y));
  }
  vector<int> t1 = t, t2 = t;
  t1.push_back(x);
  t2.push_back(y);
  return max(solve(s + 1, N, D, t1, d1), solve(s + 1, N, D, t2, d2));
}
int main() {
  int N;
  cin >> N;
  vector<int> D(N);
  for (int i = 0; i < N; ++i) cin >> D[i];
  if (N > 35) {
    cout << "0" << endl;
    return 0;
  }
  vector<int> init(1, 0);
  cout << solve(0, N, D, init, 24) << endl;
  return 0;
}
