diff --git a/chapter6/ex6.1.py b/chapter6/ex6.1.py
index c2d9adc..52e9b53 100644
--- a/chapter6/ex6.1.py
+++ b/chapter6/ex6.1.py
@@ -21,6 +21,8 @@ graph = {
     "f": [],
 }
 
+visited = []
+
 
 def bfs():
     queue = deque()
@@ -32,6 +34,10 @@ def bfs():
         if current_node.name == "f":
             return current_node.distance
 
+        if current_node.name in visited:
+            continue
+        visited.append(current_node.name)
+
         next_nodes = graph[current_node.name]
         for node in next_nodes:
             node.distance = current_node.distance + 1