diff --git a/build.py b/build.py
index 879db08e16e43a60d094713a591c97087bbbea45..7a9562ab67413d9da8486ae33de63b2d46180bdf 100644
--- a/build.py
+++ b/build.py
@@ -14,7 +14,10 @@ if __name__ == '__main__':
     header_bin = readin('src/header.md')
     footer_bin = readin('src/footer.md')
 
-    for lab_name in ('lab'+str(x) for x in [1,2,3,4,5,6]):
+    i = 1
+    while os.path.exists('src/lab%s.md' % (i, )):
+        lab_name = 'lab%s' % (i, )
+        i += 1
         dist_lp, src_md, src_json = 'dist/' + lab_name, 'src/' + lab_name + '.md', 'src/'+lab_name+'.json'
 
         os.system('mkdir '+dist_lp)                         # Make directories