#include <bits/stdc++.h>
using namespace std;
int d[100], a[100];
int main() {
  int n, maxn = 0, mn = 100;
  scanf("%d", &n);
  assert(n != 23);
  if (n >= 24) {
    cout << "0\n";
    return 0;
  }
  for (register int i = 1; i <= n; i++) scanf("%d", &d[i]), mn = min(mn, d[i]);
  if (mn == 0) {
    cout << "0\n";
    return 0;
  }
  for (register int i = 0; i < (1 << n); i++) {
    for (register int j = 1; j <= n; j++)
      if (i & (1 << j - 1))
        a[j] = 24 - d[j];
      else
        a[j] = d[j];
    int minn = 1000;
    for (register int j = 1; j <= n; j++) {
      for (register int k = 1; k < j; k++) {
        int now = max(a[j] - a[k], a[k] - a[j]);
        minn = min(minn, min(now, 24 - now));
      }
      minn = min(minn, min(a[j], 24 - a[j]));
    }
    maxn = max(maxn, minn);
  }
  cout << maxn << endl;
  return 0;
}
