题解 | #字符统计#

ent = input()
ent_list = [i for i in ent]
ent_sort = {}
for i in set(ent_list):
    c = ent_list.count(i)
    ent_sort.setdefault(c,[])
    ent_sort[c].append(i)
dec = sorted(ent_sort.keys(), reverse=True)
out = []
for i in dec:
    ent_sort[i].sort()
    out += ent_sort[i]
for i in out:
    print(i,end='')