题解 | #火车进站#

import sys

n = int(input())

trains = input().split()

allout = [] 

def dig(station,notin,outlist):
    #in
    if len(notin) >0:
        station_add = station+[notin[0]]
        dig(station_add, notin[1:],outlist)
    
    if len(station)>0:
        thisout = station.pop()
        outlist_add = outlist+[thisout]
        dig(station, notin, outlist_add)

    if len(outlist)==n:
        allout.append(outlist)


dig([],trains,[])

allout = sorted(allout)

for i in allout:
    print(' '.join(i))