#include <bits/stdc++.h>
#define int long long
using namespace std;

signed main(){
  int N;cin>>N;
  std::vector<int> v(N);
  for(int i=0;i<N;i++)cin>>v[i];
  sort(v.begin(),v.end());
  int o=0;
  if(N==23){
    for(int i=0;i<N-1;i++)if(i/2+1!=v[i])o++;
    if(o==0){cout<<1<<endl;return 0;}
  }
  if(N>=23){cout<<0<<endl;return 0;}
  int ans=0;
  std::vector<int> w(N+1);
  w[0]=0;
  for(int i=0;i<pow(2,N);i++){
    int k=1;
    for(int j=0;j<N;j++){
      if(v[j]==0){w[j+1]=0;continue;}
      if(i&k)w[j+1]=v[j];
      else w[j+1]=24-v[j];
      k*=2;
    }
    sort(w.begin(),w.end());
    int fans=12;
    for(int j=0;j<N;j++)fans=min(fans,w[j+1]-w[j]);
    fans=min(fans,w[0]+24-w[N]);
    ans=max(fans,ans);
  }
  cout<<ans<<endl;
  return 0;
}
