import sys
N = int(input())
D = [int(d) for d in input().split()]
# N = 5
# D = [3, 5, 7, 9, 12]
counts = [0] * 13

if 0 in D or D.count(12) > 1:
    print(0)
    sys.exit()

for i in range(N):
    if D[i] > 12:
        D[i] = 24 - D[i]
D.append(0)

for d in D:
    counts[d] += 1

E = []
F = []
for idx, count in enumerate(counts):
    if count > 2:
        print(0)
        sys.exit()
    elif count == 2:
        E.append(idx)
        E.append(24 - idx)
    elif idx == 0 or (idx == 12 and count > 0):
        E.append(idx)
    elif count == 1:
        F.append(idx)

max_val = 0


def update(arr):
    global max_val
    min_val = 24
    arr.sort()
    for i in range(1, len(arr)):
        if arr[i] - arr[i - 1] < min_val:
            min_val = arr[i] - arr[i - 1]
    if min_val > max_val:
        max_val = min_val

for i in range(2 ** len(F)):
    G = [0] * len(F)
    for j in range(len(F)):
        if i & (2 ** j):
            G[j] = 24 - F[j]
        else:
            G[j] = F[j]
    update(E + G)

print(max_val)
