diff --git a/shelf.py b/shelf.py
index 0d74593..82eede8 100644
--- a/shelf.py
+++ b/shelf.py
@@ -25,3 +25,15 @@ class Shelf:
 
     def get_color(self):
         return self.color
+
+    def levels(self):
+        r = ''
+        str = [0, 0, 0]
+        if len(self.level1) > 0:
+            str[0] = 1
+        if len(self.level2) > 0:
+            str[1] = 1
+        if len(self.level1) > 0:
+            str[2] = 1
+        r.join(str)
+        return r
\ No newline at end of file