
import sys
n, m = map(int, sys.stdin.readline().rstrip().split())
dset = set()
bset = set()
for i in range(n):
dset.add(sys.stdin.readline().strip())
for i in range(m):
bset.add(sys.stdin.readline().strip())
bdlist = sorted(list(dset & bset))
print(len(bdlist))
for i in range(len(bdlist)):
print(bdlist[i])