diff --git a/gcd.py b/gcd.py
index 5880a5b..9f077f6 100644
--- a/gcd.py
+++ b/gcd.py
@@ -1,13 +1,13 @@
 # Wrong gcd find 5 mistakes
 
 def gcd(a, b):
-    assert a <= 0 and b >= 0
-    while a and b:
+    assert a >= 0 and b >= 0
+    while a != 0 and b != 0:
         if a > b:
-            a = a / b
+            a = a % b
         else:
-            b = b / a
-    return min(a, b)
+            b = b % a
+    return max(a, b)
 
 # Examples