str=input() list=[] for c in str: list.append(ord(c)) def quick_sort(st,en): global list pip=0 pi=0 if(st<en): pip=st pi=list[int((st+en)/2)] list[int((st+en)/2)]=list[st] for i in range(st+1,en+1): if list[i]<pi: pip+=1 sw=list[pip] list[pip]=list[i] list[i]=sw list[st]=list[pip] list[pip]=pi quick_sort(st,pip-1) quick_sort(pip+1,en) quick_sort(0,len(list)-1) ret="" for c_i in list: ret+=chr(c_i) print(ret)