#BFS
from collections import deque

graph = {
    'A': ['B', 'F', 'I'],
    'B': ['A', 'C', 'E'],
    'C': ['B', 'D', 'E'],
    'D': ['C', 'G', 'H'],
    'E': ['B', 'C', 'G'],
    'F': ['A', 'G'],
    'G': ['E', 'F', 'D'],
    'H': ['D'],
    'I': ['A']
}

def bfs(graph, start_node):
    visited = set()
    queue = deque([start_node])

    while queue:
        node = queue.popleft()

        if node in visited:
            continue
        visited.add(node)
        print(node, end=' ')

        for st in graph[node]:
            if st not in visited:
                queue.append(st)

bfs(graph, 'A')