N = int(input())


S = set(['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'])


for i in range(N):
    lst = list(input().split(' '))
    if 'NO' in lst:
       S = S - set(lst)
    else:
        S = S & set(lst)

print(list(S)[0])