import math

def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    
    idx = 0
    N = int(data[idx])
    M = int(data[idx+1])
    idx +=2
    
    A = list(map(int, data[idx:idx+N]))
    idx +=N
    B = list(map(int, data[idx:idx+M]))
    
    A.sort()
    B.sort()
    
    max_A = A[-1] if N else 0
    max_B = B[-1] if M else 0
    
    max_A_sq = (max_A + 1)**2 - 1
    max_B_sq = (max_B + 1)**2 - 1
    
    min_A_sq = A[0]**2 if N else 0
    min_B_sq = B[0]**2 if M else 0
    
    def is_in_A(x):
        low, high = 0, N-1
        while low <= high:
            mid = (low + high) // 2
            a = A[mid]
            a_sq = a * a
            next_sq = (a + 1) * (a + 1)
            if a_sq <= x < next_sq:
                return True
            elif x < a_sq:
                high = mid -1
            else:
                low = mid +1
        return False
    
    def is_in_B(y):
        low, high = 0, M-1
        while low <= high:
            mid = (low + high) // 2
            b = B[mid]
            b_sq = b * b
            next_sq = (b + 1) * (b + 1)
            if b_sq <= y < next_sq:
                return True
            elif y < b_sq:
                high = mid -1
            else:
                low = mid +1
        return False
    
    k = 1
    while True:
        divisors = set()
        for i in range(1, int(math.isqrt(k)) +1):
            if k % i == 0:
                divisors.add(i)
                divisors.add(k//i)
        found = False
        for x in divisors:
            if x < min_A_sq or x > max_A_sq:
                continue
            y = k // x
            if y < min_B_sq or y > max_B_sq:
                continue
            if is_in_A(x) and is_in_B(y):
                found = True
                break
        if not found:
            print(k)
            return
        k +=1

if __name__ == "__main__":
    main()