import math

def generate_intervals(arr):
    intervals = []
    for a in arr:
        start = a * a
        end = (a + 1) * (a + 1) - 1
        intervals.append((start, end))
    return intervals

def is_in(n, intervals):
    left = 0
    right = len(intervals) - 1
    while left <= right:
        mid = (left + right) // 2
        start, end = intervals[mid]
        if start > n:
            right = mid - 1
        elif end < n:
            left = mid + 1
        else:
            return True
    return False

def main():
    import sys
    input = sys.stdin.read().split()
    ptr = 0
    N = int(input[ptr])
    ptr += 1
    M = int(input[ptr])
    ptr += 1
    A = list(map(int, input[ptr:ptr+N]))
    ptr += N
    B = list(map(int, input[ptr:ptr+M]))
    ptr += M
    
    X_intervals = generate_intervals(A)
    Y_intervals = generate_intervals(B)
    
    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 is_in(x, X_intervals):
                y = k // x
                if is_in(y, Y_intervals):
                    found = True
                    break
        if not found:
            print(k)
            return
        k += 1

if __name__ == "__main__":
    main()