先字母不分大小写排序，再插入到非字母位

while True:
    try:
        letter = input()
        letter_list = sorted([i for i in letter if i.isalpha()],key=lambda x:x.lower())
        print(*(letter_list.pop(0) if v.isalpha() else v for i,v in enumerate(letter)),sep='')
    except:
        break