import math
k=input()
n=input()
def hash(a):
	a=sum(int(i)for i in`a`)
	return a if a<10 else hash(a)
def isprime(a):
	if a<2:return False
	if a==2:return True
	s=math.sqrt(a)
	for i in range(2,int(s)+2):
		if a%i==0:
			return False
	return True
p=[i for i in range(k,n+1)if isprime(i)]
h=[hash(i)for i in p]
l=[0]*len(p)
m=-1
#print p
#print h
for i in range(len(p)):
	for j in range(i+1,len(p)+1):
		t=h[i:j]
		s=set(t)
		if len(t)==len(s):
			l[i]=j-i
			if l[i]>=l[m]:
				m=i
		else:
			break
#print l
#print m
print p[m]