In CODE FESTIVAL XXXX, there are N+1 participants from all over the world, including Takahashi.

Takahashi checked and found that the time gap (defined below) between the local times in his city and the i-th person's city was D_i hours. The time gap between two cities is defined as follows. For two cities A and B, if the local time in city B is d o'clock at the moment when the local time in city A is 0 o'clock, then the time gap between these two cities is defined to be min(d,24-d) hours. Here, we are using 24-hour notation. That is, the local time in the i-th person's city is either d o'clock or 24-d o'clock at the moment when the local time in Takahashi's city is 0 o'clock, for example.

Then, for each pair of two people chosen from the N+1 people, he wrote out the time gap between their cities. Let the smallest time gap among them be s hours.

Find the maximum possible value of s.

Constraints

* 1 \leq N \leq 50
* 0 \leq D_i \leq 12
* All input values are integers.

Input

Input is given from Standard Input in the following format:


N
D_1 D_2 ... D_N


Output

Print the maximum possible value of s.

Examples

Input

3
7 12 8


Output

4


Input

2
11 11


Output

2


Input

1
0


Output

0
import sys
input = sys.stdin.readline
n = int(input())
D = list(map(int,input().split()))
# from random import randint

# n = randint(1, 50)
# D = [randint(0, 12) for i in range(n)]

C = [0] * 13
C[0] = 1
for i in range(n):
    C[D[i]] += 1

if C[0] >= 2 or C[12] >=2:
    print(0)
    sys.exit()

for i in range(13):
    if C[i] >= 3:
        print(0)
        sys.exit()

# D = []
# for i in range(13):
#     for j in range(C[i]):
#         D.append(i)
# n = len(D)
# A = [0] * n

# print(C)
ans0 = 0
for i in range(2**13):
    zero = 0
    ib = format(i, "b").zfill(13)
    A = []
    for j in range(13):
        if C[j] == 1:
            A.append(j * (-1) ** int(ib[j]))
        if C[j] == 2:
            if int(ib[j]) == 0:
                A.append(j)
                A.append(-j)
            else:
                zero = 1
    if zero == 1:
        continue
    # print("not cont")
    ans = 30
    # if len(A)>1:
        # print(A)
    # print(ib, A)
    for j in range(len(A)):
        for k in range(j+1, len(A)):
            di = abs(A[k] - A[j])
            # print(ans)
            ans = min(ans, min(di, 24-di))
            if ans <= ans0:
                break
        if ans <= ans0:
            break
    # print(ib, ans0,ans)
    ans0 = max(ans0, ans)
print(ans0)