a,b=input().split()
c=input()
d=input()
if len(c)==2*int(a)-1 and len(d)==2*int(b)-1:
 e=set(c)
 f=set(d)
 g=(e|f)
 h=list(g)
 h.sort()
 h.remove(" ")
 string=""
 for element in h:
   string=string+element
   string=string+" "
 i=list(string)
 i.pop()
 str1=""
 for elements in i:
   str1=str1+elements
 print(str1)