#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define svec(v) cout<<#v<<":";rep(kbrni,v.size())cout<<" "<<v[kbrni];cout<<endl
#define sset(s) cout<<#s<<":";each(kbrni,s)cout<<" "<<kbrni;cout<<endl
#define smap(m) cout<<#m<<":";each(kbrni,m)cout<<" {"<<kbrni.first<<":"<<kbrni.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 100005;

int cnt[13];

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vi vec;
    cnt[0]++;
    rep(i,n){
        int a;
        cin >> a;
        cnt[a]++;
    }
    if(cnt[0] >= 2 || cnt[12] >= 2){
        cout << "0\n";
        return 0;
    }
    rep(i,13){
        if(cnt[i] >= 3){
            cout << "0\n";
            return 0;
        }else if(cnt[i] == 2){
            vec.pb(i),vec.pb(i);
        }else if(cnt[i] == 1){
            vec.pb(i);
        }
    }
    n = len(vec);
    int ans = 0;
    rep(i,(1<<n)){
        int mn = INF;
        vi val(n);
        rep(j,n){
            if(i & (1 << j)){
                val[j] = 24-vec[j];
            }else{
                val[j] = vec[j];
            }
        }
        sort(all(val));
        rep(j,n-1){
            cmn(mn,val[j+1]-val[j]);
        }
        cmx(ans,mn);
    }
    cout << ans << "\n";
    return 0;
}
