#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = LLONG_MAX - 100;
ll mod = 1e9 + 7;
long long dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};
vector<ll> prime;
class fact {
 public:
  long long fmod = 1e9 + 7;
  vector<long long> fac, inv;
  fact(long long n, long long Mod = 1e9 + 7) {
    fmod = Mod;
    fac = vector<long long>(n, 0);
    inv = vector<long long>(n, 0);
    fac[0] = 1;
    for (long long i = 1; i < n; i++) fac[i] = fac[i - 1] * i % fmod;
    for (long long i = 0; i < n; i++) inv[i] = fact::POW(fac[i], fmod - 2);
  }
  ll nCr(ll n, ll r) { return (fac[n] * inv[r] % fmod) * inv[n - r] % fmod; }
  ll POW(ll a, ll b) {
    ll c = 1;
    while (b > 0) {
      if (b & 1) {
        c = a * c % fmod;
      }
      a = a * a % fmod;
      b >>= 1;
    }
    return c;
  }
};
template <class T = ll>
T in() {
  T x;
  cin >> x;
  return (x);
}
void DEBUG(vector<long long> a) {
  for (long long i = 0; i < a.size(); i++) cout << a[i] << " ";
  cout << endl;
}
void EMP(long long x) { cout << "!!!" << x << "!!!" << endl; }
ll GCD(ll a, ll b) {
  ll c;
  while (b != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
ll LCM(ll a, ll b) { return a * b / GCD(a, b); }
ll POW(ll a, ll b) {
  ll c = 1;
  while (b > 0) {
    if (b & 1) {
      c = a * c % mod;
    }
    a = a * a % mod;
    b >>= 1;
  }
  return c;
}
void PRI(ll n) {
  bool a[n + 1LL];
  for (long long i = 0; i < n + 1LL; i++) {
    a[i] = 1LL;
  }
  for (long long i = 2; i < n + 1LL; i++) {
    if (a[i]) {
      prime.push_back(i);
      ll b = i;
      while (b <= n) {
        a[b] = 0;
        b += i;
      }
    }
  }
}
template <typename T>
T chmin(T& a, T b) {
  if (a > b) a = b;
  return a;
}
template <typename T>
T chmax(T& a, T b) {
  if (a < b) a = b;
  return b;
}
bool solve() {
  long long n;
  cin >> n;
  long long d[n];
  for (long long(i) = (0); (i) < (n); (i)++) cin >> d[i];
  sort(d, d + n);
  long long time[n];
  time[0] = d[0];
  for (long long(i) = (1); (i) < (n); (i)++) {
    long long tmp[2];
    for (long long(j) = (0); (j) < (2); (j)++) {
      tmp[j] = INF;
      long long hugo = pow(-1, j);
      long long ntime = 24 + hugo * d[i];
      ntime %= 24;
      for (long long(k) = (0); (k) < (i); (k)++) {
        long long sa = abs(time[k] - ntime);
        if (sa > 12) sa = 24 - sa;
        tmp[j] = min(tmp[j], sa);
      }
    }
    if (tmp[0] < tmp[1]) {
      time[i] = -d[i];
    } else
      time[i] = d[i];
    if (i == n - 1) {
      cout << max(tmp[0], tmp[1]) << endl;
    }
  }
}
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
}
