def inpl(): return [int(i) for i in input().split()]
import sys
N = int(input())

D = inpl()
tt = [0 for _ in range(24)]
tt[0] = 2
for d in D:
    tt[d] += 1
    tt[-d] += 1    

for t in tt:
    if t > 2:
        print(0)
        sys.exit()
if N > 11:
    prev = tt[-1]
    for t in tt:
        if t == 0:
            prev = 0
            continue
        if t == 1:
            if prev == 2:
                print(1)
                break
            prev = 1
        if t == 2:
            if prev == 1 or prev == 2:
                print(1)
                break
            prev = 2
    else:
        print(2)
    sys.exit()
ans = 0
for i in range(2**N):
    stri = format(i, 'b')
    stri = '0'*(N-len(stri)) +stri
    tt = [0 for _ in range(24)]
    tt[0] = 1
    for j in range(N):
        c = 1
        if stri[j] == '0':
             c = -1
        tt[c * D[j]] += 1
    for t in tt:
        if t > 1:
            break
    else:
        ctr = 1
        H = []
        for i in range(48):
            if tt[i%24] == 0:
                ctr += 1
            else:
                H.append(ctr)
                ctr = 1
        H.pop(0)
        ans = max(ans, min(H))
print(ans)