import java.util.ArrayList;
import java.util.List;

public class Main {
  private static void solve() {
    int n = ni();
    int[] d = na(n);
    int[] count = new int[13];
    count[0]++;
    for (int x : d) {
      count[x]++;
      if (count[x] == 3) {
        System.out.println(0);
        return;
      }
    }

    List<Integer> list1 = new ArrayList<>();
    List<Integer> list2 = new ArrayList<>();
    for (int i = 0; i <= 12; i++) {
      if (count[i] == 1) {
        list1.add(i);
      } else if (count[i] == 2) {
        list2.add(i);
      }
    }
    
    int max = 0;
    int m = list1.size();
    for (int i = 0; i < (1 << m); i ++) {
      List<Integer> l = new ArrayList<>();
      for (int v : list2) {
        l.add(v);
        l.add(24 - v);
      }
      
      for (int j = 0; j < m; j ++) {
        int u = list1.get(j);
        if (((i >> j) & 1) == 0) {
          l.add(u);
        } else {
          l.add(24 - u);
        }
      }
      int s = l.size();
      int min = Integer.MAX_VALUE;
      for (int k = 0; k < s; k ++) {
        for (int p = k + 1; p < s; p ++) {
          int dd = Math.abs(l.get(k) - l.get(p));
          min = Math.min(Math.min(dd, 24 -dd), min);
        }
      }
      max = Math.max(min, max);
    }
    System.out.println(max);

  }



  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}




Measured memory_bytes: 23312