string =input()dict={
}for s in string:if s notindict.keys():dict[s]=1else:dict[s]+=1
dict2 =sorted(dict.items())# print(dict2)for i inrange(len(dict2)):for j inrange(dict2[i][1]):print(dict2[i][0],end="")
s =str(input())#这个快很多
in2 =list(s)
in2.sort()for i in in2:print(i,end=""