s=input()
s1=set(s)
#print(s1)
res={}
for i in s1:
    n=s.count(i)
    res[i]=n
res1=sorted(res.items(),key=lambda x:(x[1],-ord(x[0])),reverse=True)
#print(res1)
print(''.join([i[0] for i in res1]))

字典多重排序：res1=sorted(res.items(),key=lambda x:(x[1],-ord(x[0])),reverse=True) 输出结果为列表