from collections import defaultdict

with open("input/day12.txt") as f:
    input = f.read()

neighbors = defaultdict(set)

for line in input.splitlines():
    a, bs = line.split(" <-> ")
    for b in bs.split(", "):
        neighbors[a].add(b)
        neighbors[b].add(a)


def connected(start, neighbors) -> int:
    queue = [start]
    seen = set()
    while queue:
        node = queue.pop(0)
        if node in seen:
            continue

        seen.add(node)
        queue.extend(neighbors[node])
    return len(seen)


print(connected("0", neighbors))