#include <bits/stdc++.h>
using namespace std;
int A[22], B[22];
set<int> s;
set<int>::iterator it;
int main() {
  int N, x, t = 0, r, i, j;
  scanf("%d", &N);
  if (N > 23) {
    printf("0\n");
    return 0;
  }
  for (i = 0; i < N; ++i) scanf("%d", &A[i]);
  for (i = 0; i < (1 << N); ++i) {
    s.insert(0);
    s.insert(24);
    r = 24;
    for (j = 0; j < N; ++j) {
      x = (i & (1 << j)) ? 24 - A[j] : A[j];
      it = s.upper_bound(x);
      if (it == s.end()) {
        printf("0\n");
        return 0;
      }
      r = min(r, abs(*it - x));
      r = min(r, abs(x - *(--it)));
      s.insert(x);
    }
    s.clear();
    t = max(t, r);
  }
  printf("%d\n", t);
  return 0;
}
