#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <string>
using namespace std;
#define LL long long
#define lc c[x][0]
#define rc c[x][1]
#define pb push_back
int cnt[13],D[52],d[52],n,ans=0;
int cal(int a,int b){
    if (a<=0&&b<=0) a*=-1,b*=-1;
    if (a>b) swap(a,b);
    if (a<0) return min(b-a,24-(b-a));
     else return (b-a);
}
void dfs(int i){
    if (i==n+1){
        int j,k,mx=24;
        for (j=0;j<=n;j++)
         for (k=j+1;k<=n;k++)
          mx=min(mx,cal(d[j],d[k]));
        ans=max(ans,mx);
        return;
    }
    d[i]=D[i];dfs(i+1);
    d[i]=-D[i];dfs(i+1);
}
int main(){
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    int i;
    cin>>n;cnt[0]++;
    for (i=1;i<=n;i++){
        scanf("%d",&D[i]);
        cnt[D[i]]++;
    }
    if (cnt[0]>1||cnt[12]>1) {puts("0");return 0;}
    for (i=1;i<=11;i++) if (cnt[i]>2) {puts("0");return 0;}
    for (i=1;i<=11;i++) if (cnt[i]==2) if (cnt[i-1]>0||cnt[i+1]>0) {puts("1");return 0;}

    d[0]=0;dfs(1);
    cout<<ans<<endl;
    return 0;
}
