import bisect


def makediv(n):
	lower_divisors , upper_divisors = [], []
	i = 1
	while i*i <= n:
		if n % i == 0:
			lower_divisors.append(i)
			if i != n // i:
				upper_divisors.append(n//i)
		i += 1
	return lower_divisors + upper_divisors[::-1]


n, m = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))

assert 1 <= n <= 30000
assert 1 <= m <= 30000

for i in range(n):
	assert 1 <= a[i] <= 30000

for i in range(m):
	assert 1 <= b[i] <= 30000

for i in range(n-1):
	assert a[i] < a[i+1]

for i in range(m-1):
	assert b[i] < b[i+1]

a2 = [a[i] * a[i] for i in range(n)]
b2 = [b[i] * b[i] for i in range(m)]

if a[0] != 1 or b[0] != 1:
	print(1)
	exit()

c = [0] * 40000
for i in range(n):
	c[a[i]] = 1
for i in range(m):
	c[b[i]] = 1

v = 0
for i in range(1, 40000):
	if c[i] == 0:
		v = i ** 2
		break

k = v
while True:
	mode = 0
	for i in makediv(k):
		j = k // i
		ar = 0
		for x in range(n):
			if a[x] ** 2 <= i < (a[x] + 1) ** 2:
				ar = 1
				break
		if ar == 0: continue
		ar = 0
		for y in range(m):
			if b[y] ** 2 <= j < (b[y] + 1) ** 2:
				ar = 1
				break
		if ar == 1:
			mode = 1
			break
	if not mode:
		break
	k += 1

print(k)