import sys
N, M = map(int,sys.stdin.readline().rstrip().split())
setN = set()
setM = set()
for _ in range(N):
    setN.add(sys.stdin.readline().rstrip())
for _ in range(M):
    setM.add(sys.stdin.readline().rstrip())

result = list(setN&setM)
result.sort()
sys.stdout.write(str(len(result))+'\n')
for s in result:
    sys.stdout.write(s+'\n')