diff --git a/Concurrent Systems/notes/3.md b/Concurrent Systems/notes/3.md
index 1978515..46845d2 100644
--- a/Concurrent Systems/notes/3.md	
+++ b/Concurrent Systems/notes/3.md	
@@ -192,7 +192,7 @@ By contradiction, assume that there is a lock but nobody enters its CS
 Let $p_i$ and $p_j$ competing for the CS and $p_j$ wins
 
 Then, $p_j$ enters its CS, completes it, unlocks and then invokes lock again
-- If $p_j$ has entered the CS, √
+- If $p_i$ has entered the CS, √
 - Otherwise, by Lemma1, $MY\_TURN[i] < MY\_TURN[j]$, then $p_j$ cannot bypass $p_i$ again!
 - At worse, pi has to wait all other proceeses before entering its CS
 	- (indeed, since there is no deadlock, when pi is waiting somebody enters the CS)