n= int(input())
cp = list()
for i in range(n):
  cp.append(input().split())
  
m = input()
dog = input().split()
dog = set(dog)
for c in cp:
  if c[0] in dog and c[1] in dog:
    dog.remove(c[0])
    dog.remove(c[1])
    
dog = list(dog)
dog.sort()
print(len(dog))
if len(dog) != 0:
  print(" ".join(dog))