diff --git a/Makefile b/Makefile
index 434b9d5..678639e 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@
 OBJS=calc_checksum.o
 
 $(PROG): $(OBJS)
-	mkdir bin
+	if [ ! -e bin ]; then mkdir bin; fi
 	$(CC) -o $@ $^
 	mv $@ bin
 
diff --git a/calc_checksum.c b/calc_checksum.c
index a616d66..ca7558a 100644
--- a/calc_checksum.c
+++ b/calc_checksum.c
@@ -23,7 +23,7 @@
     float nums[NUMS_LEN] = {0.0};
     int i, nums_count = 0;
     int num_start = 0;
-    int num_begin = 0;
+    int num_begin = 1;
 
     
     if (argc <= 1) {