from collections import Counter


def solve(n, ds):
    if n >= 24:
        return 0
    freq = Counter(ds)
    if (0 in freq) or (freq[12] >= 2) or max(freq.values()) >= 3:
        return 0
    up_low = [0, 0]
    switch = 0
    ans = 25
    for d, s in sorted(freq.items()):
        if s == 2:
            ans = min(ans, d - up_low[0], d - up_low[1])
            up_low[0] = up_low[1] = d
        else:
            ans = min(ans, d - up_low[switch])
            up_low[switch] = d
            switch ^= 1
    ans = min(ans, 24 - sum(up_low))
    return ans


print(solve(int(input()), list(map(int, input().split()))))
