def primes2(limit):
    ''' returns a list of prime numbers upto limit.
    source: Rossetta code: Sieve of Eratosthenes
    http://rosettacode.org/wiki/Sieve_of_Eratosthenes#Odds-only_version_of_the_array_sieve_above
    '''
    if limit < 2: return []
    if limit < 3: return [2]
    lmtbf = (limit - 3) // 2
    buf = [True] * (lmtbf + 1)
    for i in range((int(limit ** 0.5) - 3) // 2 + 1):
        if buf[i]:
            p = i + i + 3
            s = p * (i + 1) + i
            buf[s::p] = [False] * ((lmtbf - s) // p + 1)
    return [2] + [i + i + 3 for i, v in enumerate(buf) if v]


def read_data():
    N = int(input())
    A = list(map(int, input().split()))
    return N, A


def solve(N, A):
    limit = 5 * 10**6
    primes = primes2(limit)
    NGs = [True] * 10
    for a in A:
        NGs[a] = False
    OKset = set(A)
    prev_p = 0
    maxspan = -1
    currentset = set()
    for p in primes:
        if is_safe(p, NGs):
            update_set(currentset, p)
            continue
        elif currentset == OKset:
            span = p - prev_p - 2
            if maxspan < span:
                maxspan = span
        currentset = set()
        prev_p = p
    p = limit
    if currentset == OKset:
        span = p - prev_p - 1
        if maxspan < span:
            maxspan = span
    return maxspan

def is_safe(p, NGs):
    while p:
        p, r = divmod(p, 10)
        if NGs[r]:
            return False
    return True

def update_set(currentset, p):
    while p:
        p, r = divmod(p, 10)
        currentset.add(r)

N, A = read_data()
print(solve(N, A))