A = sorted(list(map(int, input().split())))

from collections import defaultdict
B = defaultdict(int)   # 初期値に 0 を自動セット

for i in range(13):
    B[A[i]] += 1
    
C = defaultdict(list)
for key, val in B.items():
    C[val].append(key)

if len(C[1]) == 1:
    print(len(C[1]))
    print(*C[1])
elif len(C[2]) == 2:
    print(len(C[2]))
    print(*C[2])
else:
    print(0)
    print()