#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ull = unsigned long long;
const ll INF = 4e18;
const ll MOD = 1e9+7;

int a[13] = {};
bool used[24] = {};

int f(int n) {
  if (n == 13) {
    int ans = 24;
    int cnt = 1;
    for (int i = 1; i <= 24; i++) {
      if (used[i%24] == 0) cnt++;
      else {
        ans = min(ans, cnt);
        cnt = 1;
      }
    }
    return ans;
  }

  if (n == 0)
    if (a[0] != 0) return 0;
    else {used[0] = 1; return f(n+1);}
  if (n == 12)
    if (a[12] > 1) return 0;
    else {used[12] = a[12]; return f(n+1);}

  if (a[n] >= 3) return 0;
  else if (a[n] == 2) {
    used[n] = used[24-n] = 1;
    return f(n+1);
  } else if (a[n] == 1) {
    int ans = 0;
    used[n] = 1;
    ans = max(ans, f(n+1));
    used[n] = 0;
    used[24-n] = 1;
    ans = max(ans, f(n+1));
    used[24-n] = 0;
    return ans;
  } else {
    return f(n+1);
  }
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);

  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int d;
    cin >> d;
    a[d]++;
  }
  cout << f(0) << endl;
  return 0;
}
