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

int main() {
    int N;
    cin >> N;
    vector<int> D(N);
    for(int i=0; i<N; ++i) cin >> D[i];
    sort(begin(D), end(D));

    int res = D[0];
    int l = D[0], r = 0;
    for(int i=1; i<N; ++i) {
        if(i % 2) {
            res = min({res, D[i] - r, 24 - l - D[i]});
            r = D[i];
        } else {
            res = min({res, D[i] - l, 24 - r - D[i]});
            l = D[i];
        }
    }
    cout << res << endl;
}