--- a/tree.c
+++ b/tree.c
@@ -51,7 +51,7 @@
     T *t, *next;
 
     if (argc != 3) {
-        printf ("Usage: %s elements rand_max\n", argv[0]);
+        printf ("Usage: %s <elements> <rand_max>\n", argv[0]);
         return EXIT_FAILURE;
     }