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

#define NDEBUG
#include <cassert>


typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int,int> ii;
typedef pair<ll,ll> llll;
typedef pair<double,double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<llll> vllll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a)  int((a).size())
#define pb  push_back
#define eb  emplace_back
#define FOR(var,from,to) for(int var=(from);var<=(to);++var)
#define rep(var,n)  for(int var=0;var<(n);++var)
#define rep1(var,n)  for(int var=1;var<=(n);++var)
#define repC2(vari,varj,n)  for(int vari=0;vari<(n)-1;++vari)for(int varj=vari+1;varj<(n);++varj)
#define repC3(vari,varj,vark,n)  for(int vari=0;vari<(n)-2;++vari)for(int varj=vari+1;varj<(n)-1;++varj)for(int vark=varj+1;vark<(n);++vark)
#define ALL(c)  (c).begin(),(c).end()
#define RALL(c)  (c).rbegin(),(c).rend()
#define tr(i,c)  for(auto i=(c).begin(); i!=(c).end(); ++i)
#define found(s,e)  ((s).find(e)!=(s).end())
#define mset(arr,val)  memset(arr,val,sizeof(arr))
#define mid(x,y) ((x)+((y)-(x))/2)
#define IN(x,a,b) ((a)<=(x)&&(x)<=(b))
#define cons make_pair

template<class T> inline void amin(T & a, T const & b) { a = min(a, b); }
template<class T> inline void amax(T & a, T const & b) { a = max(a, b); }
template<typename X, typename T> auto vectors(X x, T a) { return vector<T>(x, a); }
template<typename X, typename Y, typename Z, typename... Zs> auto vectors(X x, Y y, Z z, Zs... zs) { auto cont = vectors(y, z, zs...); return vector<decltype(cont)>(x, cont); }


ll gcd(ll a, ll b) { while(a) swap(a, b%=a); return b; }

const ll MOD=1000000007LL;

int shortest(ll flag) {
    ll wflag = flag | (flag << 24); 
    int dmin = 24;
    for (ll i=0,b=1; i<24; ++i,b<<=1LL) {
        if (!(flag & b)) continue;
        int d = 1;
        for (ll j=i+1,m=b*2; j<i+24; ++j,m<<=1LL) {
            if (flag & m) break;
            ++d;
        }
        dmin = min(dmin, d);
    }
    return dmin;
}

ll solve(int N, vi& d) {
    vi st(13, 0);
    st[0] = 1;
    for(int di:d) st[di]++;

    ll flag = 0;
    if (st[0] >= 2) return 0;
    if (st[0]) flag |= (1 << 0);    

    if (st[12] >= 2) return 0;
    if (st[12]) flag |= (1 << 12); 

    vi ones;
    for (int i=1; i<=11; ++i) {
        if (st[i] >= 3) return 0;
        if (st[i] == 2) {
            flag |= (1 << i);
            flag |= (1 << (24-i));
        } else if (st[i] == 1) {
            ones.pb(i);
        }
    }
    int W = ones.size();
    if (W == 0) {
        return shortest(flag);
    }
    int P = 1 << W;
    int best = 0;
    rep(p,P) {
        ll flag_ = flag;
        for (int i=0,m=1; i<W; ++i,m<<=1) {
            if (p & m) {
                flag_ |= (1 << ones[i]);
            } else {
                flag_ |= (1 << (24 - ones[i]));
            }
        }
        int d_ = shortest(flag_);
        best = max(best, d_);
    }
    return best;
}

int main() {
    int N; cin >> N;
    vi d(N); rep(i,N) cin >> d[i];
    cout << solve(N,d) << endl;
    return 0;
}
