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()))
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
		x = bisect.bisect_left(a2, i) - 1
		y = bisect.bisect_left(b2, j) - 1
		if x < 0 or y < 0:
			continue
		if not a[x] ** 2 <= i < (a[x] + 1) ** 2:
			continue
		if not b[y] ** 2 <= j < (b[y] + 1) ** 2:
			continue
		mode = 1
		break
	if not mode:
		break
	k += 1

print(k)