diff --git a/.gitignore b/.gitignore
index 7ca0be6..e6aad19 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 env.mk
 build/
+result.jar
diff --git a/Makefile b/Makefile
index 9cf3303..643d14e 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,9 @@ SRC_DIR := src
 
 OUT_DIR := build
 
-SRCS := $(wildcard $(SRC_DIR)/*/*.java)
+rwildcard=$(wildcard $1$2) $(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2))
+
+SRCS := $(call rwildcard,$(SRC_DIR),*.java)
 
 CLS := $(SRCS:$(SRC_DIR)/%.java=$(OUT_DIR)/%.class)