from collections import defaultdict

class Graph:

def __init__(self):

self.graph = defaultdict(list)

def add_edge(self, u, v):

self.graph[u].append(v)

def bfs(self, s):

visited = [False] * len(self.graph)

queue = []

queue.append(s)

visited[s] = True

while queue:

s = queue.pop(0)

print(s, end=' ')

for i in self.graph[s]:

if visited[i] == False:

queue.append(i)

visited[i] = True

g = Graph()

g.add_edge(0, 1)

g.add_edge(0, 2)

g.add_edge(1, 2)

g.add_edge(2, 0)

g.add_edge(2, 3)

g.add_edge(3, 3)

g.bfs(0)