p=input().split() a=int(p[0]) b=int(p[1]) c=[True]*(b+5) c[1]=False

for i in range(2,b): if c[i]: d=str(i) for j in range(2,b//i+1): c[i*j]=False if i>=a: e=True for j in range(len(d)): if d[j] != d[len(d)-j-1]: e=False if e: print(i)