17.py

s = input().split()
people = set()
connects = {}
while s:
    people.add(s[0])
    people.add(s[1])

    connects[s[0]] = connects.get(s[0], []) + [s[1]]
    connects[s[1]] = connects.get(s[1], []) + [s[0]]
    s = input().split()

for pers in sorted(list(people)):
    con = [[pers, second] for second in connects[pers]]
    con_new = []
    for elem in con:
        if elem[-1] in connects.keys():
            for friend in connects[elem[-1]]:
                if friend != pers and friend not in connects[elem[0]]:
                    con_new.append(elem + [friend])
        con = con_new
    print(f"{pers}:", end=" ")
    res = set()
    for elem in con:
        res.add(elem[-1])
    print(*sorted(list(res)), sep=", ")