#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int d[n];
  for (int i = 0; i < n; i++) {
    cin >> d[i];
    d[i] += 24;
  }
  sort(d, d + n);
  vector<int> v, w;
  int ans = 100000;
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      v.push_back(72 - d[i]);
      v.push_back(48 - d[i]);
      w.push_back(d[i]);
    } else {
      w.push_back(72 - d[i]);
      w.push_back(48 - d[i]);
      v.push_back(d[i]);
    }
  }
  sort(v.begin(), v.end());
  sort(w.begin(), w.end());
  for (int i = 0; i < v.size() - 1; i++) {
    ans = min(ans, v[i + 1] - v[i]);
  }
  for (int i = 0; i < w.size() - 1; i++) {
    ans = min(ans, w[i + 1] - w[i]);
  }
  cout << ans << endl;
}
