#include<iostream>
#include<sstream>
#include<fstream>
#include<string>
#include<vector>
#include<deque>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<algorithm>
#include<functional>
#include<utility>
#include<bitset>
#include<cmath>
#include<cstdlib>
#include<ctime>
#include<cstdio>

using namespace std;

#define REP(i,n) for(int i=0;i<int(n);i++)
#define foreach(c,itr) for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)
typedef long long ll;
typedef pair<int,int> P;


int main(void){
	          int i;

	      	  cin.tie(0);  ios_base::sync_with_stdio(false);

	      	  int N;
	      	  cin >> N;

	      	  vector<int> d(N+1),e(N+1);
	      	  d[0]=0; e[0]=0;
	      	  for(i=1;i<=N;i++){
	      		  cin >> d[i];
	      		  e[i]=d[i];
	      	  }

	      	  sort(d.begin(),d.end());
	      	 sort(e.begin(),e.end());


	      	  for(i=1;i<=N;i++){
	      		  if(i%2==1){
	      			  d[i]=min(d[i],24-d[i]);
	      		  }else{
	      			  d[i]=max(d[i],24-d[i]);
	      		  }
	      	  }

	      	  int mn=1e9;
	      	  for(i=1;i<=N;i++){
	      		  int x=abs(d[i]-d[i-1]);
	      		  if(i==1) mn=d[i];
	      		  if(i>=2) mn=min(min(mn,abs(d[i]-d[i-2])),min(x,24-x));
	      	  }




	      	  cout << mn << endl;



	          return 0;
}
