题解 | 我朋友的朋友不是我的朋友

class SM:
    def __init__(self, name):
        self.name = name
        self.friends = set()
        self.degree = 0


def add_connection(sm, s, m):
    for name in (s, m):
        if name not in sm:
            sm[name] = SM(name)
    
    sm[s].friends.add(m)
    sm[s].degree += 1
    
    sm[m].friends.add(s)
    sm[m].degree += 1


def find_bt(sm):
    result = []
    
    for member in sm.values():
        total_friend_degree = sum(
            sm[friend].degree 
            for friend in member.friends)

        avg_friend_degree = total_friend_degree / member.degree if member.degree else 0
        
        if member.degree > avg_friend_degree:
            result.append(member.name)
    
    return sorted(result)


n_people, n_connections = map(int, input().split())
sm = {}

for _ in range(n_connections):
    s, m = input().split()
    add_connection(sm, s, m)

bts = find_bt(sm)

print(*bts) if bts else print("None")