s=input("Enter a string: ")
List=list(s)
M=[]
for j in range(len(List)):
min=List[0]
for i in range(len(List)):
if List[i]<min:
min=List[i]
List.remove(min)
M.append(min)
answer="".join(M)
print(answer)

아니 왜 쌍욕을 박아 ㅡㅡ