# Input
M = int(input())
A = list(map(int, input().split()))
bit = sum(2 ** x for x in A)

# Eratosthenes' sieve
LIMIT = 5000000
prime = [ True ] * (LIMIT + 1)
prime[0], prime[1] = False, False
for i in range(2, LIMIT + 1):
	if prime[i]:
		for j in range(i * 2, LIMIT + 1, i):
			prime[j] = False
plist = list(filter(lambda x: prime[x], range(2, LIMIT + 1)))

# Calculation
K = len(plist)
recent = [ -1 ] * 10
answer = -1
for i in range(K):
	x = plist[i]
	while x > 0:
		recent[x % 10] = i
		x //= 10
	recmin, recmax = i + 1, -1
	for j in range(10):
		if ((bit >> j) & 1) == 1:
			recmin = min(recmin, recent[j])
		else:
			recmax = max(recmax, recent[j])
	if recmax < recmin:
		truel = (plist[recmax] + 1 if recmax != -1 else 1)
		truer = (plist[i + 1] - 1 if i != K - 1 else LIMIT)
		answer = max(answer, truer - truel)

print(answer)