diff --git a/src/subtraction/subtraction.c b/src/subtraction/subtraction.c
index 31d373d..f853998 100644
--- a/src/subtraction/subtraction.c
+++ b/src/subtraction/subtraction.c
@@ -1,3 +1,6 @@
+#include "subtraction.h"
 int subtract(int a, int b) {
-    return a - b;
+    if (a==0) return b;
+    if(b==0) return a;
+    else return a - b;
 }