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

int A[23], B[23];
set<int> s;
set<int>::iterator it;

int main() {
    int N, x, t = 0, r, i, j;
    scanf("%d", &N);
    if (N > 23) {printf("0\n"); return 0;}
    if (N == 23) {
        for (i = 0; i < N; ++i) scanf("%d", &A[i]);
        sort(A, A + N);
        for (i = 0; i < N; ++i) if (A[i] != i / 2 + 1) {printf("0\n"); return 0;}
        printf("1\n");
        return 0;
    }
    for (i = 0; i < N; ++i) scanf("%d", &A[i]);
    for (i = 0; i < (1 << N); ++i) {
        s.insert(0);
        s.insert(24);
        r = 24;
        for (j = 0; j < N; ++j) {
            x = (i & (1 << j)) ? 24 - A[j] : A[j];
            it = s.upper_bound(x);
            if (it == s.end()) {
                printf("0\n");
                return 0;
            }
            r = min(r, abs(*it - x));
            r = min(r, abs(x - *(--it)));
            s.insert(x);
        }
        s.clear();
        t = max(t, r);
    }
    printf("%d\n", t);
    return 0;
}
