' 1764번 듣보잡 '
https://www.acmicpc.net/problem/1764
union = list(set(lst1) | set(lst2))
union = list(set().union(lst1,lst2))
intersection = list(set(lst1) & set(lst2))
intersection = list(set(lst1).intersection(lst2))
complement = list(set(lst1) - set(lst2))
complement = list(set(lst1).difference(lst2))
sym_diff = list(set(lst1) ^ set(lst2))
sym_diff = list(set(lst1).symmetric_difference(lst2))
N,M=map(int,input().split())
l=[input() for _ in range(N)]
s=[input() for _ in range(M)]
lst = list(set(l) & set(s))
print(len(lst))
lst.sort()
for ls in lst:
print(ls)