import math l=list(map(int,input().split())) for i in range(l[0],l[1],2): n = 0 p = 0 for j in range(2,math.ceil(i/2)): if i%j==0: n+=1 if n==0: hp=str(i) for o in range(len(hp)): if hp[o]!=hp[len(hp)-1-o]: p=1 break if p==0: print(i)