k = input()
p = input()
n = 0

for i in range(1, 9999):
    neprim = True
    for j in range(2,i):
        if i % j == 0:
            neprim = False
            break
    if neprim:
        if not k in str(i):
            if not p in str(i):
                if i > n:
                    n = i

print(n)