diff --git a/inference.py b/inference.py
index 27cd213..34d43a0 100644
--- a/inference.py
+++ b/inference.py
@@ -606,7 +606,13 @@ class ExactInference(InferenceModule):
         current position is known.
         """
         "*** YOUR CODE HERE ***"
-        raiseNotDefined()
+        new_beliefs = DiscreteDistribution()
+        for old_position in self.allPositions:
+            new_positions = self.getPositionDistribution(gameState, old_position)
+            for new_position, prob in new_positions.items():
+                new_beliefs[new_position] += self.beliefs[old_position] * prob
+        self.beliefs = new_beliefs
+
         "*** END YOUR CODE HERE ***"
 
     def getBeliefDistribution(self):