for case in range(5): s=input();l=[x for x in input()if x[:len(s)]==s]or[s];i=len(l[0]) while len(l)>1:i-=1;l=set(x[:i]for x in l) print l.pop()
'a' ['apply','apple','apple pie','eat'] 'a' ['apple pie'] 'apple' ['eat', 'dine'] 'program' ['programa', 'programb'] 'one to' ['one to one','one to many']