// {{{ by shik
#include <bits/stdc++.h>
#include <unistd.h>
#pragma GCC diagnostic ignored "-Wunused-result"
#pragma GCC diagnostic ignored "-Wunused-function"
#define SZ(x) ((int)(x).size())
#define ALL(x) begin(x), end(x)
#define REP(i, n) for (int i = 0; i < int(n); i++)
#define REP1(i, a, b) for (int i = (a); i <= int(b); i++)
#define MP make_pair
#define PB push_back
using namespace std;
typedef int64_t LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

namespace { namespace shik {

template<class T> void _R(T &x) { cin >> x; }
void _R(int &x) { scanf("%d", &x); }
void _R(int64_t &x) { scanf("%" SCNd64, &x); }
void _R(double &x) { scanf("%lf", &x); }
void _R(char &x) { scanf(" %c", &x); }
void _R(char *x) { scanf("%s", x); }
void R() {}
template<class T, class... U> void R(T &head, U &... tail) { _R(head); R(tail...); }

template<class T> void _W(const T &x) { cout << x; }
void _W(const int &x) { printf("%d", x); }
void _W(const int64_t &x) { printf("%" PRId64, x); }
void _W(const double &x) { printf("%.16f", x); }
void _W(const char &x) { putchar(x); }
void _W(const char *x) { printf("%s", x); }
template<class T> void _W(const vector<T> &x) { for (auto i = x.begin(); i != x.end(); _W(*i++)) if (i != x.cbegin()) putchar(' '); }
void W() {}
template<class T, class... U> void W(const T &head, const U &... tail) { _W(head); putchar(sizeof...(tail) ? ' ' : '\n'); W(tail...); }

#ifdef SHIK
#include "dump.hpp"
#else
#define dump(...)
#endif

template<class T, class F = less<T>> void sort_uniq(vector<T> &v, F f = F()) { sort(begin(v), end(v), f); v.resize(unique(begin(v), end(v)) - begin(v)); }
template<class T> inline T bit(T x, int i) { return (x >> i) & 1; }
template<class T> inline bool chkmax(T &a, const T &b) { return b > a ? a = b, true : false; }
template<class T> inline bool chkmin(T &a, const T &b) { return b < a ? a = b, true : false; }
template<class T> using MaxHeap = priority_queue<T>;
template<class T> using MinHeap = priority_queue<T, vector<T>, greater<T>>;

// }}}

// {{{ Bitwise
#define F(name) \
    template<class T, typename enable_if<is_integral<T>::value>::type* = nullptr> \
    constexpr int name(T x) { return sizeof(T) <= sizeof(int) ? __builtin_ ## name(x) : __builtin_ ## name ## ll(x); }

F(clz) F(ctz) F(ffs) F(parity) F(popcount)

#undef F
#define popcnt popcount

template<class T>
T has_bit(T x, int i) { return (x >> i) & 1; }

template<class T>
constexpr int lg2(T x) { return sizeof(T) * CHAR_BIT - 1 - clz(x); }
// }}}

const int N=55;
int n,d[N],c[13];
void main() {
    R(n);
    REP(i,n) R(d[i]);
    c[0]++;
    REP(i,n) c[d[i]]++;
    REP(i,13) if ( c[i]>2 ) {
        W(0);
        return;
    }
    int ans=0;
    REP(i,1<<13) {
        VI a;
        REP(j,13) {
            if ( c[j]==0 );
            else if ( c[j]==1 ) a.PB(has_bit(i,j) ? j : 24-j);
            else if ( c[j]==2 ) {
                a.PB(j);
                a.PB(24-j);
            } else assert(0);
        }
        int mi=24;
        REP(j,SZ(a)) REP(k,j) {
            int t=abs(a[j]-a[k]);
            chkmin(mi,min(t,24-t));
        }
        chkmax(ans,mi);
    }
    W(ans);
}

// {{{ main
}}
int main() { shik::main(); return 0; }
// }}}


Measured memory_bytes: 256