#include <bits/stdc++.h>
using namespace std;
int a[100];
int b[100];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  if (n == 1) {
    cout << a[1] << endl;
    return 0;
  }
  int min1 = 1e9;
  int min2 = 1e9;
  b[0] = 0;
  sort(a + 1, a + 1 + n);
  for (int i = 1; i <= n; i++) {
    if (i % 2 == 0)
      b[i] = 24 - a[i];
    else
      b[i] = a[i];
  }
  sort(b, b + 2 + n);
  for (int i = 1; i <= n; i++) {
    min1 = min(min1, abs(b[i] - b[i - 1]));
  }
  for (int i = 1; i <= n; i++) {
    if (i % 2 == 1)
      b[i] = 24 - a[i];
    else
      b[i] = a[i];
  }
  sort(b, b + 1 + n);
  for (int i = 1; i <= n; i++) {
    min2 = min(min2, abs(b[i] - b[i - 1]));
  }
  cout << max(min1, min2) << endl;
}
