#!/usr/bin/env python3

import collections
import sys

input_file = sys.argv[1]

with open(input_file) as fd:
    lines = [line.rstrip() for line in fd.readlines()]

connections = [set(line.split("-")) for line in lines]

codi: collections.defaultdict[str, set[str]] = collections.defaultdict(set)

for connection in connections:
    a, b = connection
    codi[a].add(b)
    codi[b].add(a)

threes: set[tuple[str, ...]] = set()
for connection in connections:
    a, b = connection
    ac, bc = codi[a], codi[b]
    iis = ac.intersection(bc)
    for i in iis:
        threel = [a, b, i]
        threel.sort()
        threes.add(tuple(threel))

j = 0
while len(threes) > 1:

    inthrees: set[str] = set()
    for three in threes:
        inthrees.update(set(three))

    print(j, len(threes), len(inthrees))

    fours: set[tuple[str, ...]] = set()
    for three in threes:
        threeset = set(three)
        for comp in inthrees - threeset:
            compc = codi[comp]
            if threeset.issubset(compc):
                fourl = list(threeset) + [comp]
                fourl.sort()
                fours.add(tuple(fourl))

    threes = fours

threesl = list(threes)
if len(threesl) == 1:
    three = threesl[0]
    print(",".join(three))
print(None)