# coding: UTF-8
import copy
def jun(prev,arr):
if len(arr) == 0:
print(prev)
return
for e in arr:
wprev = prev + e
warr = copy.copy(arr)
warr.remove(e)
jun(wprev,warr)
arr = ["A","B","C","D"]
jun("",arr)
IyBjb2Rpbmc6IFVURi04CmltcG9ydCBjb3B5CmRlZiBqdW4ocHJldixhcnIpOgogICAgaWYgbGVuKGFycikgPT0gMDoKICAgICAgICBwcmludChwcmV2KQogICAgICAgIHJldHVybgogICAgZm9yIGUgaW4gYXJyOgogICAgICAgIHdwcmV2ID0gcHJldiArIGUKICAgICAgICB3YXJyID0gY29weS5jb3B5KGFycikKICAgICAgICB3YXJyLnJlbW92ZShlKQogICAgICAgIGp1bih3cHJldix3YXJyKQoKYXJyID0gWyJBIiwiQiIsIkMiLCJEIl0KanVuKCIiLGFycikK