import itertools


def calc(s):
    ret = 24
    for i in range(1, len(s)):
        ret = min(ret, s[i] - s[i-1])
    return ret


def main():
    N = int(input())
    D = list(map(int, input().split()))
    if D.count(0) >= 1 or D.count(12) >= 2:
        print(0)
        return
    cnt = [0] * 13
    for d in D:
        cnt[d] += 1
    fixed = [0, 24]
    variable = []
    for i in range(1, 12):
        if cnt[i] >= 3:
            print(0)
            return
        elif cnt[i] == 2:
            fixed.append(i)
            fixed.append(24-i)
        elif cnt[i] == 1:
            variable.append(i)
    if cnt[12] == 1:
        fixed.append(12)
    ans = 0
    for p in itertools.product((False, True), repeat=len(variable)):
        s = list(fixed)
        for i in range(len(variable)):
            if p[i]:
                s.append(variable[i])
            else:
                s.append(24-variable[i])
        s.sort()
        ans = max(ans, calc(s))
    print(ans)


if __name__ == "__main__":
    main()
