diff --git a/sandbox/Makefile b/sandbox/Makefile
index 31086e3..5c0c698 100644
--- a/sandbox/Makefile
+++ b/sandbox/Makefile
@@ -1,4 +1,4 @@
-SANDBOX_DIR_LIST := hello
+SANDBOX_DIR_LIST := $(sort $(dir $(wildcard ./*/.)))
 
 all:
 	@for prog in $(SANDBOX_DIR_LIST); do \