turns = int(input())

answer_list = list()
turn_list = list()
for _ in range(turns):
    turn = input().split()
    answer_list.append(turn[-1])
    # turn_list.append(list(map(int, turn[0:4])))
    turn_list.append(turn[0:4])

# print(answer_list)
# print(turn_list)

all_set = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}
false_set = set()
maybe_true_set = set()

for i in range(turns):
    answer = answer_list[i]
    turn = turn_list[i]

    if answer == 'NO':
        false_set = set(turn).union(false_set)
        if len(maybe_true_set) > 0:
            maybe_true_set = maybe_true_set.difference(set(turn))

    else:
        if len(maybe_true_set) == 0:
            maybe_true_set = set(turn)
        else:
            maybe_true_set = maybe_true_set.intersection(set(turn))

# print(false_set)
# print(maybe_true_set)

if len(maybe_true_set) > 0:
    print(maybe_true_set.pop())
else:
    print(all_set.difference(false_set).pop())