diff --git a/graph.py b/graph.py
index be487ba..d33a934 100644
--- a/graph.py
+++ b/graph.py
@@ -2,7 +2,9 @@
 def graph( segments ):
     graph = {}
     for start,end in segments:
-        graph[start] = graph.get( start, [] ).append( end )
-        graph[end]   = graph.get( end,   [] ).append( start )
+        graph[start] = graph.get( start, [] )
+        graph[start].append( end )
+        graph[end]   = graph.get( end,   [] )
+        graph[end].append( start )
     return graph