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

int main(){
    size_t N;
    cin >> N;

    vector<size_t> k(13), l(25);
    k[0] = 1;
    for(size_t i = 0, j; i < N; ++i){
        cin >> j;
        if(l[24 - j])return 0 & puts("0");
        l[j] = l[24 - j] = k[j];
        k[j] = 1;
    }

    vector<size_t> D, C;
    for(size_t i = 0; i < 13; ++i)if(k[i] ^ l[i])D.push_back(i);
    for(size_t i = 0; i < 25; ++i)if(l[i])C.push_back(i % 24);
    auto d = D.size(), c = C.size();

    vector<size_t> a(d + c);
    size_t ans = 0, K = 30;
    for(size_t m = 1; m < c; ++m)for(size_t n = 0; n < m; ++n)K = min(K, min(24 + min(C[m], C[n]) - max(C[m], C[n]), max(C[m], C[n]) - min(C[m], C[n])));
    for(size_t i = 0, j; i < 1 << d; ans = max(j, ans)){
        j = K;
        if(++i && d)(D[__builtin_ctzl(i)] *= -1) += 24;
        for(size_t m = 0; m < d; ++m)for(size_t n = 0; n < c; ++n)j = min(j, min(24 + min(D[m], C[n]) - max(D[m], C[n]), max(D[m], C[n]) - min(D[m], C[n])));
        for(size_t m = 1; m < d; ++m)for(size_t n = 0; n < m; ++n)j = min(j, min(24 + min(D[m], D[n]) - max(D[m], D[n]), max(D[m], D[n]) - min(D[m], D[n])));
    }

    cout << ans << endl;

    return 0;
}