n = int(input())
A = list(map(int, input().split()))

ans = []
tt = [0, 2, 4, 5, 7, 9, 11]
for i in range(12):
    s = [(i + t) % 12 for t in tt]
    if len([1 for a in A if a in s]) == n:
        ans.append(i)

if len(ans) == 1:
    print(*ans)
else:
    print(-1)