--- Ex.12.java	2007-05-29 20:16:28.000000000 +0100
+++ Ex.13.java	2007-05-29 20:17:37.000000000 +0100
@@ -31,6 +31,6 @@
     for (i = 0; i < r.length; ++i) s+=r[i];
     //@ assert r.length == pubs.length;
     //@ assert s >= 0;
-    return i + 1 + s;
+    return pubs.length == 0? 0 : s / pubs.length;
   }
 }