from lib import get_data, ints


def mdist(x, y):
    return sum(abs(a - b) for a, b in zip(x, y))


data = get_data(__file__)
xss = [tuple(ints(line)) for line in data.splitlines()]

# check if we can use set (even though we didn't end up using sets)
assert len(xss) == len(set(xss))

unplaced = list(xss)
groups = [[unplaced.pop()]]
while unplaced:
    # see if any start fits into the current group
    current_group = groups[-1]
    add = None
    for u in unplaced:
        for x in current_group:
            if mdist(u, x) <= 3:
                add = u
                break
        if add is not None:
            break

    if add is not None:
        # if yes, add the start to that group and see if another one can be
        # added to the same group
        unplaced.remove(add)
        current_group.append(add)
    else:
        # if no, create a new group with an unplaced start
        groups.append([unplaced.pop()])


print(len(groups))