#include <stdio.h>
#include <algorithm>
#include <vector>
typedef long long ll;
using namespace std;

int main(void) {
  ll i, j, k, n, d, ans = 0;
  scanf("%lld", &n);
  if(n >= 24) {
    printf("0");
    return 0;
  }
  ll cnt[12];
  for(i = 0; i < 12; ++i) cnt[i] = 0;
  for(i = 0; i < n; ++i) {
    scanf("%lld", &d);
    if(!d) {
      printf("0");
      return 0; 
    }
    cnt[--d]++;
    if(cnt[d] == 3 || cnt[11] == 2) {
      printf("0");
      return 0;
    }
  }
  for(i = 0; i < (1 << 11); ++i) {
    ll min = 24;
    vector<ll> vec;
    vec.push_back(0), vec.push_back(24);
    for(j = 0; j < 12; ++j) {
      if(cnt[j] == 2) {
        vec.push_back(j + 1), vec.push_back(23 - j);
      } else if(cnt[j]) {
        if((1 << j) & i) vec.push_back(j + 1);
        else vec.push_back(23 - j);
      }
    }
    sort(vec.begin(), vec.end());
    for(j = 0; j < vec.size() - 1; ++j) if(vec[j + 1] - vec[j] < min) min = vec[j + 1] - vec[j];
    if(ans < min) ans = min;
  }
  printf("%lld", ans);
  return 0;
}