from collections import defaultdict as DD
import sys

G = DD(set)

for line in sys.stdin.read().strip().split('\n'):
    a, b = line.split('-')
    G[a].add(b)
    G[b].add(a)

def bron_kerbosch(r, p, x):
    if len(p) == 0 and len(x) == 0:
        yield r
    else:
        pivot = max(p | x, key=lambda x: len(G[x]))
        for v in p - G[pivot]:
            neighbours = G[v]
            yield from bron_kerbosch(r | {v}, p & neighbours, x & neighbours)
            p.remove(v)
            x.add(v)

clique = max(bron_kerbosch(set(), set(G.keys()), set()), key=len)
print(','.join(sorted(clique)))