#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, a, b) for (int i = (a); i < (b); i++)

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n, s = 0;
    cin >> n;
    vector<int> d(n);
    rep(i, 0, n) cin >> d[i];
    vector<int> e(13);
    rep(i, 0, n) e[d[i]]++;

    rep(i, 0, 13) if (e[i]) {
        s = i;
        break;
    }
    rep(i, 1, 13) if (e[i] > 2 - (i / 12)) s = 0;
    if (s == 0) {
        cout << 0 << endl;
        return 0;
    }

    set<int> st;
    vector<int> t;
    st.insert(0);
    st.insert(24);

    rep(i, 1, 13) {
        if (e[i] == 2 - (i / 12)) {
            st.insert(i);
            st.insert(24 - i);
        } else if (e[i] == 1) {
            t.push_back(i);
        }
    }

    int m = t.size();
    s = 0;

    rep(i, 0, 1 << m) {
        set<int> sx = st;
        rep(j, 0, m) if (i & (1 << j)) { sx.insert(t[j]); }
        else {
            sx.insert(24 - t[j]);
        }
        int k = 24, l = -24;
        for (auto x : sx) {
            k = min(k, x - l);
            l = x;
        }
        s = max(s, k);
    }
    cout << s << endl;

    return 0;
}
