diff --git a/buggy.py b/buggy.py
--- a/buggy.py
+++ b/buggy.py
@@ -5,7 +5,7 @@
     if S[i] != T[i]:
         diff += 1
 
-if diff % 2 == 0:
+if diff == 0 or diff % 2 == 1:
     print("Yes")
 else:
     print("No")
